Creates an instance of GPIOAccess.
-ポート番号
-ポート
-GPIO チェンジイベントハンドラ
-Sets or gets the default captureRejection value for all emitters.
-This symbol shall be used to install a listener for only monitoring 'error'
-events. Listeners installed using this symbol are called before the regular
-'error' listeners are called.
Installing a listener using this symbol does not change the behavior once an
-'error' event is emitted, therefore the process will still crash if no
-regular 'error' listener is installed.
ポート情報取得処理
-現在のポート情報
-Alias for emitter.on(eventName, listener).
Synchronously calls each of the listeners registered for the event namedeventName, in the order they were registered, passing the supplied arguments
+
GPIO
+Creates an instance of GPIOAccess.
+Optionalports: GPIOPortMapポート番号
+GPIO チェンジイベントハンドラ
+StaticcaptureValue: boolean
+Change the default captureRejections option on all new EventEmitter objects.
Static ReadonlycaptureValue: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler.
StaticdefaultBy default, a maximum of 10 listeners can be registered for any single
+event. This limit can be changed for individual EventEmitter instances
+using the emitter.setMaxListeners(n) method. To change the default
+for allEventEmitter instances, the events.defaultMaxListeners property
+can be used. If this value is not a positive number, a RangeError is thrown.
Take caution when setting the events.defaultMaxListeners because the
+change affects all EventEmitter instances, including those created before
+the change is made. However, calling emitter.setMaxListeners(n) still has
+precedence over events.defaultMaxListeners.
This is not a hard limit. The EventEmitter instance will allow
+more listeners to be added but will output a trace warning to stderr indicating
+that a "possible EventEmitter memory leak" has been detected. For any single
+EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to
+temporarily avoid this warning:
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
// do stuff
emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});
+The --trace-warnings command-line flag can be used to display the
+stack trace for such warnings.
The emitted warning can be inspected with process.on('warning') and will
+have the additional emitter, type, and count properties, referring to
+the event emitter instance, the event's name and the number of attached
+listeners, respectively.
+Its name property is set to 'MaxListenersExceededWarning'.
Static ReadonlyerrorThis symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.
Installing a listener using this symbol does not change the behavior once an 'error' event is emitted. Therefore, the process will still crash if no
+regular 'error' listener is installed.
ポート情報取得処理
+現在のポート情報
+Optional[captureRest...args: AnyRestAlias for emitter.on(eventName, listener).
Rest...args: any[]Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments
to each.
Returns true if the event had listeners, false otherwise.
const EventEmitter = require('events');
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener
-Returns an array listing the events for which the emitter has registered +
Returns true if the event had listeners, false otherwise.
import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener
+Rest...args: AnyRestReturns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbols.
const EventEmitter = require('events');
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});
const sym = Symbol('symbol');
myEE.on(sym, () => {});
console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
-Returns the current max listener value for the EventEmitter which is either
-set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.
Returns the number of listeners listening to the event named eventName.
The name of the event being listened for
-Returns a copy of the array of listeners for the event named eventName.
server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
-Alias for emitter.removeListener().
Adds the listener function to the end of the listeners array for the
-event named eventName. No checks are made to see if the listener has
-already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple
-times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
-import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});
const sym = Symbol('symbol');
myEE.on(sym, () => {});
console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
+Returns the current max listener value for the EventEmitter which is either
+set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.
Returns the number of listeners listening for the event named eventName.
+If listener is provided, it will return how many times the listener is found
+in the list of the listeners of the event.
The name of the event being listened for
+Optionallistener: FunctionThe event handler function
+Returns a copy of the array of listeners for the event named eventName.
server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
+Alias for emitter.removeListener().
Rest...args: any[]Adds the listener function to the end of the listeners array for the event
+named eventName. No checks are made to see if the listener has already
+been added. Multiple calls passing the same combination of eventName and
+listener will result in the listener being added, and called, multiple times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependListener() method can be used as an alternative to add the
+
By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
-The name of the event.
-The callback function
-Adds a one-timelistener function for the event named eventName. The
+
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
+The name of the event.
+The callback function
+Rest...args: any[]Adds a one-time listener function for the event named eventName. The
next time eventName is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
-server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the
+
By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
-The name of the event.
-The callback function
-Adds the listener function to the beginning of the listeners array for the
+
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
+The name of the event.
+The callback function
+Rest...args: any[]Adds the listener function to the beginning of the listeners array for the
event named eventName. No checks are made to see if the listener has
-already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple
-times.
server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
-eventName
+and listener will result in the listener being added, and called, multiple times.
+server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
The name of the event.
-The callback function
-Adds a one-timelistener function for the event named eventName to the_beginning_ of the listeners array. The next time eventName is triggered, this
+
The name of the event.
+The callback function
+Rest...args: any[]Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this
listener is removed, and then invoked.
server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
-server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
The name of the event.
-The callback function
-Returns a copy of the array of listeners for the event named eventName,
+
The name of the event.
+The callback function
+Rest...args: any[]Returns a copy of the array of listeners for the event named eventName,
including any wrappers (such as those created by .once()).
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));
// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];
// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();
// Logs "log once" to the console and removes the listener
logFnWrapper();
emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');
// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
-Removes all listeners, or those of the specified eventName.
It is bad practice to remove listeners added elsewhere in the code, +
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));
// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];
// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();
// Logs "log once" to the console and removes the listener
logFnWrapper();
emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');
// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
+Removes all listeners, or those of the specified eventName.
It is bad practice to remove listeners added elsewhere in the code,
particularly when the EventEmitter instance was created by some other
component or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter, so that calls can be chained.
Removes the specified listener from the listener array for the event namedeventName.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
-OptionaleventName: string | symbolRemoves the specified listener from the listener array for the event named eventName.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
+removeListener() will remove, at most, one instance of a listener from the
listener array. If any single listener has been added multiple times to the
listener array for the specified eventName, then removeListener() must be
called multiple times to remove each instance.
Once an event is emitted, all listeners attached to it at the
-time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and_before_ the last listener finishes execution will
-not remove them fromemit() in progress. Subsequent events behave as expected.
const myEmitter = new MyEmitter();
const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};
const callbackB = () => {
console.log('B');
};
myEmitter.on('event', callbackA);
myEmitter.on('event', callbackB);
// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B
// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A
-removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution
+will not remove them fromemit() in progress. Subsequent events behave as expected.
+import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();
const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};
const callbackB = () => {
console.log('B');
};
myEmitter.on('event', callbackA);
myEmitter.on('event', callbackB);
// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B
// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A
+Because listeners are managed using an internal array, calling this will
change the position indices of any listener registered after the listener
being removed. This will not impact the order in which listeners are called,
@@ -142,81 +184,103 @@ but it means that any copies of the listener array as returned by
the emitter.listeners() method will need to be recreated.
When a single function has been added as a handler multiple times for a single
event (as in the example below), removeListener() will remove the most
-recently added instance. In the example the once('ping')listener is removed:
const ee = new EventEmitter();
function pong() {
console.log('pong');
}
ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);
ee.emit('ping');
ee.emit('ping');
-once('ping') listener is removed:
+import { EventEmitter } from 'node:events';
const ee = new EventEmitter();
function pong() {
console.log('pong');
}
ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);
ee.emit('ping');
ee.emit('ping');
+Returns a reference to the EventEmitter, so that calls can be chained.
By default EventEmitters will print a warning if more than 10 listeners are
+
Rest...args: any[]By default EventEmitters will print a warning if more than 10 listeners are
added for a particular event. This is a useful default that helps finding
memory leaks. The emitter.setMaxListeners() method allows the limit to be
-modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
Unexport all exported GPIO ports.
+modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
ポート開放結果
-Returns a copy of the array of listeners for the event named eventName.
For EventEmitters this behaves exactly the same as calling .listeners on
+
ポート開放結果
+StaticaddExperimentalListens once to the abort event on the provided signal.
Listening to the abort event on abort signals is unsafe and may
+lead to resource leaks since another third party with the signal can
+call e.stopImmediatePropagation(). Unfortunately Node.js cannot change
+this since it would violate the web standard. Additionally, the original
+API makes it easy to forget to remove listeners.
This API allows safely using AbortSignals in Node.js APIs by solving these
+two issues by listening to the event such that stopImmediatePropagation does
+not prevent the listener from running.
Returns a disposable so that it may be unsubscribed from more easily.
+import { addAbortListener } from 'node:events';
function example(signal) {
let disposable;
try {
signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
disposable = addAbortListener(signal, (e) => {
// Do something when signal is aborted.
});
} finally {
disposable?.[Symbol.dispose]();
}
}
+Disposable that removes the abort listener.
StaticgetReturns a copy of the array of listeners for the event named eventName.
For EventEmitters this behaves exactly the same as calling .listeners on
the emitter.
For EventTargets this is the only way to get the event listeners for the
event target. This is useful for debugging and diagnostic purposes.
const { getEventListeners, EventEmitter } = require('events');
{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
getEventListeners(ee, 'foo'); // [listener]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
getEventListeners(et, 'foo'); // [listener]
}
-A class method that returns the number of listeners for the given eventNameregistered on the given emitter.
const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2
-The emitter to query
-The event name
-```js -const { on, EventEmitter } = require('events');
-(async () => { - const ee = new EventEmitter();
-// Emit later on - process.nextTick(() => { - ee.emit('foo', 'bar'); - ee.emit('foo', 42); - });
-for await (const event of on(ee, 'foo')) { - // The execution of this inner block is synchronous and it - // processes one event at a time (even with await). Do not use - // if concurrent execution is required. - console.log(event); // prints ['bar'] [42] - } - // Unreachable here -})();
-
Returns an `AsyncIterator` that iterates `eventName` events. It will throw
if the `EventEmitter` emits `'error'`. It removes all listeners when
exiting the loop. The `value` returned by each iteration is an array
composed of the emitted event arguments.
An `AbortSignal` can be used to cancel waiting on events:
```js
const { on, EventEmitter } = require('events');
const ac = new AbortController();
(async () => {
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();
process.nextTick(() => ac.abort());
-The name of the event being listened for
-that iterates eventName events emitted by the emitter
Creates a Promise that is fulfilled when the EventEmitter emits the given
-event or that is rejected if the EventEmitter emits 'error' while waiting.
+
import { getEventListeners, EventEmitter } from 'node:events';
{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
}
+StaticgetReturns the currently set max amount of listeners.
+For EventEmitters this behaves exactly the same as calling .getMaxListeners on
+the emitter.
For EventTargets this is the only way to get the max event listeners for the
+event target. If the number of event handlers on a single EventTarget exceeds
+the max set, the EventTarget will print a warning.
import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';
{
const ee = new EventEmitter();
console.log(getMaxListeners(ee)); // 10
setMaxListeners(11, ee);
console.log(getMaxListeners(ee)); // 11
}
{
const et = new EventTarget();
console.log(getMaxListeners(et)); // 10
setMaxListeners(11, et);
console.log(getMaxListeners(et)); // 11
}
+StaticlistenerA class method that returns the number of listeners for the given eventName registered on the given emitter.
import { EventEmitter, listenerCount } from 'node:events';
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2
+The emitter to query
+The event name
+Staticonimport { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo')) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
+Returns an AsyncIterator that iterates eventName events. It will throw
+if the EventEmitter emits 'error'. It removes all listeners when
+exiting the loop. The value returned by each iteration is an array
+composed of the emitted event arguments.
An AbortSignal can be used to cancel waiting on events:
import { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ac = new AbortController();
(async () => {
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();
process.nextTick(() => ac.abort());
+Use the close option to specify an array of event names that will end the iteration:
import { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
ee.emit('close');
});
for await (const event of on(ee, 'foo', { close: ['close'] })) {
console.log(event); // prints ['bar'] [42]
}
// the loop will exit after 'close' is emitted
console.log('done'); // prints 'done'
+Optionaloptions: StaticEventEmitterIteratorOptionsAn AsyncIterator that iterates eventName events emitted by the emitter
Optionaloptions: StaticEventEmitterIteratorOptionsStaticonceCreates a Promise that is fulfilled when the EventEmitter emits the given
+event or that is rejected if the EventEmitter emits 'error' while waiting.
The Promise will resolve with an array of all the arguments emitted to the
given event.
This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event
-semantics and does not listen to the 'error' event.
const { once, EventEmitter } = require('events');
async function run() {
const ee = new EventEmitter();
process.nextTick(() => {
ee.emit('myevent', 42);
});
const [value] = await once(ee, 'myevent');
console.log(value);
const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});
try {
await once(ee, 'myevent');
} catch (err) {
console.log('error happened', err);
}
}
run();
-The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the
-'error' event itself, then it is treated as any other kind of event without
+
This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event
+semantics and does not listen to the 'error' event.
import { once, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
process.nextTick(() => {
ee.emit('myevent', 42);
});
const [value] = await once(ee, 'myevent');
console.log(value);
const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});
try {
await once(ee, 'myevent');
} catch (err) {
console.error('error happened', err);
}
+The special handling of the 'error' event is only used when events.once() is used to wait for another event. If events.once() is used to wait for the
+'error' event itself, then it is treated as any other kind of event without
special handling:
const { EventEmitter, once } = require('events');
const ee = new EventEmitter();
once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.log('error', err.message));
ee.emit('error', new Error('boom'));
// Prints: ok boom
-import { EventEmitter, once } from 'node:events';
const ee = new EventEmitter();
once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.error('error', err.message));
ee.emit('error', new Error('boom'));
// Prints: ok boom
+An AbortSignal can be used to cancel waiting for the event:
const { EventEmitter, once } = require('events');
const ee = new EventEmitter();
const ac = new AbortController();
async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}
foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
-Generated using TypeDoc
import { EventEmitter, once } from 'node:events';
const ee = new EventEmitter();
const ac = new AbortController();
async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}
foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
+Optionaloptions: StaticEventEmitterOptionsOptionaloptions: StaticEventEmitterOptionsStaticsetimport { setMaxListeners, EventEmitter } from 'node:events';
const target = new EventTarget();
const emitter = new EventEmitter();
setMaxListeners(5, target, emitter);
+Optionaln: numberA non-negative number. The maximum number of listeners per EventTarget event.
Rest...eventTargets: (EventTarget | EventEmitter<DefaultEventMap>)[]GPIO ポート
-Creates an instance of GPIOPort.
-ポート番号
-入出力方向
-エクスポートリトライ回数
-エクスポート
-ポーリング間隔
-ポート番号
-タイムアウト値
-入出力値
-GPIO チェンジイベントハンドラ
-Sets or gets the default captureRejection value for all emitters.
-This symbol shall be used to install a listener for only monitoring 'error'
-events. Listeners installed using this symbol are called before the regular
-'error' listeners are called.
Installing a listener using this symbol does not change the behavior once an
-'error' event is emitted, therefore the process will still crash if no
-regular 'error' listener is installed.
GPIO 入出力方向 getter
-現在のGPIO 入出力方向
-GPIO export の有無 getter
-現在のGPIO 出力
-ピン名取得処理
-現在のピン名
-ポート名取得処理
-現在のポート名
-ポート番号取得処理
-現在のポート番号
-Alias for emitter.on(eventName, listener).
Synchronously calls each of the listeners registered for the event namedeventName, in the order they were registered, passing the supplied arguments
+
GPIO ポート
+GPIO チェンジイベントハンドラ
+StaticcaptureValue: boolean
+Change the default captureRejections option on all new EventEmitter objects.
Static ReadonlycaptureValue: Symbol.for('nodejs.rejection')
See how to write a custom rejection handler.
StaticdefaultBy default, a maximum of 10 listeners can be registered for any single
+event. This limit can be changed for individual EventEmitter instances
+using the emitter.setMaxListeners(n) method. To change the default
+for allEventEmitter instances, the events.defaultMaxListeners property
+can be used. If this value is not a positive number, a RangeError is thrown.
Take caution when setting the events.defaultMaxListeners because the
+change affects all EventEmitter instances, including those created before
+the change is made. However, calling emitter.setMaxListeners(n) still has
+precedence over events.defaultMaxListeners.
This is not a hard limit. The EventEmitter instance will allow
+more listeners to be added but will output a trace warning to stderr indicating
+that a "possible EventEmitter memory leak" has been detected. For any single
+EventEmitter, the emitter.getMaxListeners() and emitter.setMaxListeners() methods can be used to
+temporarily avoid this warning:
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.setMaxListeners(emitter.getMaxListeners() + 1);
emitter.once('event', () => {
// do stuff
emitter.setMaxListeners(Math.max(emitter.getMaxListeners() - 1, 0));
});
+The --trace-warnings command-line flag can be used to display the
+stack trace for such warnings.
The emitted warning can be inspected with process.on('warning') and will
+have the additional emitter, type, and count properties, referring to
+the event emitter instance, the event's name and the number of attached
+listeners, respectively.
+Its name property is set to 'MaxListenersExceededWarning'.
Static ReadonlyerrorThis symbol shall be used to install a listener for only monitoring 'error' events. Listeners installed using this symbol are called before the regular 'error' listeners are called.
Installing a listener using this symbol does not change the behavior once an 'error' event is emitted. Therefore, the process will still crash if no
+regular 'error' listener is installed.
GPIO 入出力方向 getter
+現在のGPIO 入出力方向
+GPIO export の有無 getter
+現在のGPIO 出力
+ピン名取得処理
+現在のピン名
+ポート名取得処理
+現在のポート名
+ポート番号取得処理
+現在のポート番号
+Optional[captureRest...args: AnyRestAlias for emitter.on(eventName, listener).
Rest...args: any[]Synchronously calls each of the listeners registered for the event named eventName, in the order they were registered, passing the supplied arguments
to each.
Returns true if the event had listeners, false otherwise.
const EventEmitter = require('events');
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener
-Returns an array listing the events for which the emitter has registered +
Returns true if the event had listeners, false otherwise.
import { EventEmitter } from 'node:events';
const myEmitter = new EventEmitter();
// First listener
myEmitter.on('event', function firstListener() {
console.log('Helloooo! first listener');
});
// Second listener
myEmitter.on('event', function secondListener(arg1, arg2) {
console.log(`event with parameters ${arg1}, ${arg2} in second listener`);
});
// Third listener
myEmitter.on('event', function thirdListener(...args) {
const parameters = args.join(', ');
console.log(`event with parameters ${parameters} in third listener`);
});
console.log(myEmitter.listeners('event'));
myEmitter.emit('event', 1, 2, 3, 4, 5);
// Prints:
// [
// [Function: firstListener],
// [Function: secondListener],
// [Function: thirdListener]
// ]
// Helloooo! first listener
// event with parameters 1, 2 in second listener
// event with parameters 1, 2, 3, 4, 5 in third listener
+Rest...args: AnyRestReturns an array listing the events for which the emitter has registered
listeners. The values in the array are strings or Symbols.
const EventEmitter = require('events');
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});
const sym = Symbol('symbol');
myEE.on(sym, () => {});
console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
-GPIO 出力処理
-GPIO 入出力方向
-export 処理の完了
-Returns the current max listener value for the EventEmitter which is either
-set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.
Returns the number of listeners listening to the event named eventName.
The name of the event being listened for
-Returns a copy of the array of listeners for the event named eventName.
server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
-Alias for emitter.removeListener().
Adds the listener function to the end of the listeners array for the
-event named eventName. No checks are made to see if the listener has
-already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple
-times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
-import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => {});
myEE.on('bar', () => {});
const sym = Symbol('symbol');
myEE.on(sym, () => {});
console.log(myEE.eventNames());
// Prints: [ 'foo', 'bar', Symbol(symbol) ]
+Returns the current max listener value for the EventEmitter which is either
+set by emitter.setMaxListeners(n) or defaults to defaultMaxListeners.
Returns the number of listeners listening for the event named eventName.
+If listener is provided, it will return how many times the listener is found
+in the list of the listeners of the event.
The name of the event being listened for
+Optionallistener: FunctionThe event handler function
+Returns a copy of the array of listeners for the event named eventName.
server.on('connection', (stream) => {
console.log('someone connected!');
});
console.log(util.inspect(server.listeners('connection')));
// Prints: [ [Function] ]
+Alias for emitter.removeListener().
Rest...args: any[]Adds the listener function to the end of the listeners array for the event
+named eventName. No checks are made to see if the listener has already
+been added. Multiple calls passing the same combination of eventName and
+listener will result in the listener being added, and called, multiple times.
server.on('connection', (stream) => {
console.log('someone connected!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependListener() method can be used as an alternative to add the
+
By default, event listeners are invoked in the order they are added. The emitter.prependListener() method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
-The name of the event.
-The callback function
-Adds a one-timelistener function for the event named eventName. The
+
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.on('foo', () => console.log('a'));
myEE.prependListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
+The name of the event.
+The callback function
+Rest...args: any[]Adds a one-time listener function for the event named eventName. The
next time eventName is triggered, this listener is removed and then invoked.
server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
-server.once('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
By default, event listeners are invoked in the order they are added. Theemitter.prependOnceListener() method can be used as an alternative to add the
+
By default, event listeners are invoked in the order they are added. The emitter.prependOnceListener() method can be used as an alternative to add the
event listener to the beginning of the listeners array.
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
-The name of the event.
-The callback function
-Adds the listener function to the beginning of the listeners array for the
+
import { EventEmitter } from 'node:events';
const myEE = new EventEmitter();
myEE.once('foo', () => console.log('a'));
myEE.prependOnceListener('foo', () => console.log('b'));
myEE.emit('foo');
// Prints:
// b
// a
+The name of the event.
+The callback function
+Rest...args: any[]Adds the listener function to the beginning of the listeners array for the
event named eventName. No checks are made to see if the listener has
-already been added. Multiple calls passing the same combination of eventNameand listener will result in the listener being added, and called, multiple
-times.
server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
-eventName
+and listener will result in the listener being added, and called, multiple times.
+server.prependListener('connection', (stream) => {
console.log('someone connected!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
The name of the event.
-The callback function
-Adds a one-timelistener function for the event named eventName to the_beginning_ of the listeners array. The next time eventName is triggered, this
+
The name of the event.
+The callback function
+Rest...args: any[]Adds a one-timelistener function for the event named eventName to the beginning of the listeners array. The next time eventName is triggered, this
listener is removed, and then invoked.
server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
-server.prependOnceListener('connection', (stream) => {
console.log('Ah, we have our first user!');
});
+Returns a reference to the EventEmitter, so that calls can be chained.
The name of the event.
-The callback function
-Returns a copy of the array of listeners for the event named eventName,
+
The name of the event.
+The callback function
+Rest...args: any[]Returns a copy of the array of listeners for the event named eventName,
including any wrappers (such as those created by .once()).
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));
// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];
// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();
// Logs "log once" to the console and removes the listener
logFnWrapper();
emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');
// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
-入力値読み取り処理
-読み取り処理の完了
-Removes all listeners, or those of the specified eventName.
It is bad practice to remove listeners added elsewhere in the code, +
import { EventEmitter } from 'node:events';
const emitter = new EventEmitter();
emitter.once('log', () => console.log('log once'));
// Returns a new Array with a function `onceWrapper` which has a property
// `listener` which contains the original listener bound above
const listeners = emitter.rawListeners('log');
const logFnWrapper = listeners[0];
// Logs "log once" to the console and does not unbind the `once` event
logFnWrapper.listener();
// Logs "log once" to the console and removes the listener
logFnWrapper();
emitter.on('log', () => console.log('log persistently'));
// Will return a new Array with a single function bound by `.on()` above
const newListeners = emitter.rawListeners('log');
// Logs "log persistently" twice
newListeners[0]();
emitter.emit('log');
+Removes all listeners, or those of the specified eventName.
It is bad practice to remove listeners added elsewhere in the code,
particularly when the EventEmitter instance was created by some other
component or module (e.g. sockets or file streams).
Returns a reference to the EventEmitter, so that calls can be chained.
Removes the specified listener from the listener array for the event namedeventName.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
-OptionaleventName: string | symbolRemoves the specified listener from the listener array for the event named eventName.
const callback = (stream) => {
console.log('someone connected!');
};
server.on('connection', callback);
// ...
server.removeListener('connection', callback);
+removeListener() will remove, at most, one instance of a listener from the
listener array. If any single listener has been added multiple times to the
listener array for the specified eventName, then removeListener() must be
called multiple times to remove each instance.
Once an event is emitted, all listeners attached to it at the
-time of emitting are called in order. This implies that anyremoveListener() or removeAllListeners() calls after emitting and_before_ the last listener finishes execution will
-not remove them fromemit() in progress. Subsequent events behave as expected.
const myEmitter = new MyEmitter();
const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};
const callbackB = () => {
console.log('B');
};
myEmitter.on('event', callbackA);
myEmitter.on('event', callbackB);
// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B
// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A
-removeListener() or removeAllListeners() calls after emitting and before the last listener finishes execution
+will not remove them fromemit() in progress. Subsequent events behave as expected.
+import { EventEmitter } from 'node:events';
class MyEmitter extends EventEmitter {}
const myEmitter = new MyEmitter();
const callbackA = () => {
console.log('A');
myEmitter.removeListener('event', callbackB);
};
const callbackB = () => {
console.log('B');
};
myEmitter.on('event', callbackA);
myEmitter.on('event', callbackB);
// callbackA removes listener callbackB but it will still be called.
// Internal listener array at time of emit [callbackA, callbackB]
myEmitter.emit('event');
// Prints:
// A
// B
// callbackB is now removed.
// Internal listener array [callbackA]
myEmitter.emit('event');
// Prints:
// A
+Because listeners are managed using an internal array, calling this will
change the position indices of any listener registered after the listener
being removed. This will not impact the order in which listeners are called,
@@ -174,84 +204,105 @@ but it means that any copies of the listener array as returned by
the emitter.listeners() method will need to be recreated.
When a single function has been added as a handler multiple times for a single
event (as in the example below), removeListener() will remove the most
-recently added instance. In the example the once('ping')listener is removed:
const ee = new EventEmitter();
function pong() {
console.log('pong');
}
ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);
ee.emit('ping');
ee.emit('ping');
-once('ping') listener is removed:
+import { EventEmitter } from 'node:events';
const ee = new EventEmitter();
function pong() {
console.log('pong');
}
ee.on('ping', pong);
ee.once('ping', pong);
ee.removeListener('ping', pong);
ee.emit('ping');
ee.emit('ping');
+Returns a reference to the EventEmitter, so that calls can be chained.
By default EventEmitters will print a warning if more than 10 listeners are
+
Rest...args: any[]By default EventEmitters will print a warning if more than 10 listeners are
added for a particular event. This is a useful default that helps finding
memory leaks. The emitter.setMaxListeners() method allows the limit to be
-modified for this specific EventEmitter instance. The value can be set toInfinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
Unexport exported GPIO ports.
+modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.
Returns a reference to the EventEmitter, so that calls can be chained.
ポート開放処理の完了
-出力値書き込み処理
-読み取り処理の完了
-Returns a copy of the array of listeners for the event named eventName.
For EventEmitters this behaves exactly the same as calling .listeners on
+
ポート開放処理の完了
+StaticaddExperimentalListens once to the abort event on the provided signal.
Listening to the abort event on abort signals is unsafe and may
+lead to resource leaks since another third party with the signal can
+call e.stopImmediatePropagation(). Unfortunately Node.js cannot change
+this since it would violate the web standard. Additionally, the original
+API makes it easy to forget to remove listeners.
This API allows safely using AbortSignals in Node.js APIs by solving these
+two issues by listening to the event such that stopImmediatePropagation does
+not prevent the listener from running.
Returns a disposable so that it may be unsubscribed from more easily.
+import { addAbortListener } from 'node:events';
function example(signal) {
let disposable;
try {
signal.addEventListener('abort', (e) => e.stopImmediatePropagation());
disposable = addAbortListener(signal, (e) => {
// Do something when signal is aborted.
});
} finally {
disposable?.[Symbol.dispose]();
}
}
+Disposable that removes the abort listener.
StaticgetReturns a copy of the array of listeners for the event named eventName.
For EventEmitters this behaves exactly the same as calling .listeners on
the emitter.
For EventTargets this is the only way to get the event listeners for the
event target. This is useful for debugging and diagnostic purposes.
const { getEventListeners, EventEmitter } = require('events');
{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
getEventListeners(ee, 'foo'); // [listener]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
getEventListeners(et, 'foo'); // [listener]
}
-A class method that returns the number of listeners for the given eventNameregistered on the given emitter.
const { EventEmitter, listenerCount } = require('events');
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2
-The emitter to query
-The event name
-```js -const { on, EventEmitter } = require('events');
-(async () => { - const ee = new EventEmitter();
-// Emit later on - process.nextTick(() => { - ee.emit('foo', 'bar'); - ee.emit('foo', 42); - });
-for await (const event of on(ee, 'foo')) { - // The execution of this inner block is synchronous and it - // processes one event at a time (even with await). Do not use - // if concurrent execution is required. - console.log(event); // prints ['bar'] [42] - } - // Unreachable here -})();
-
Returns an `AsyncIterator` that iterates `eventName` events. It will throw
if the `EventEmitter` emits `'error'`. It removes all listeners when
exiting the loop. The `value` returned by each iteration is an array
composed of the emitted event arguments.
An `AbortSignal` can be used to cancel waiting on events:
```js
const { on, EventEmitter } = require('events');
const ac = new AbortController();
(async () => {
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();
process.nextTick(() => ac.abort());
-The name of the event being listened for
-that iterates eventName events emitted by the emitter
Creates a Promise that is fulfilled when the EventEmitter emits the given
-event or that is rejected if the EventEmitter emits 'error' while waiting.
+
import { getEventListeners, EventEmitter } from 'node:events';
{
const ee = new EventEmitter();
const listener = () => console.log('Events are fun');
ee.on('foo', listener);
console.log(getEventListeners(ee, 'foo')); // [ [Function: listener] ]
}
{
const et = new EventTarget();
const listener = () => console.log('Events are fun');
et.addEventListener('foo', listener);
console.log(getEventListeners(et, 'foo')); // [ [Function: listener] ]
}
+StaticgetReturns the currently set max amount of listeners.
+For EventEmitters this behaves exactly the same as calling .getMaxListeners on
+the emitter.
For EventTargets this is the only way to get the max event listeners for the
+event target. If the number of event handlers on a single EventTarget exceeds
+the max set, the EventTarget will print a warning.
import { getMaxListeners, setMaxListeners, EventEmitter } from 'node:events';
{
const ee = new EventEmitter();
console.log(getMaxListeners(ee)); // 10
setMaxListeners(11, ee);
console.log(getMaxListeners(ee)); // 11
}
{
const et = new EventTarget();
console.log(getMaxListeners(et)); // 10
setMaxListeners(11, et);
console.log(getMaxListeners(et)); // 11
}
+StaticlistenerA class method that returns the number of listeners for the given eventName registered on the given emitter.
import { EventEmitter, listenerCount } from 'node:events';
const myEmitter = new EventEmitter();
myEmitter.on('event', () => {});
myEmitter.on('event', () => {});
console.log(listenerCount(myEmitter, 'event'));
// Prints: 2
+The emitter to query
+The event name
+Staticonimport { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo')) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
+Returns an AsyncIterator that iterates eventName events. It will throw
+if the EventEmitter emits 'error'. It removes all listeners when
+exiting the loop. The value returned by each iteration is an array
+composed of the emitted event arguments.
An AbortSignal can be used to cancel waiting on events:
import { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ac = new AbortController();
(async () => {
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
});
for await (const event of on(ee, 'foo', { signal: ac.signal })) {
// The execution of this inner block is synchronous and it
// processes one event at a time (even with await). Do not use
// if concurrent execution is required.
console.log(event); // prints ['bar'] [42]
}
// Unreachable here
})();
process.nextTick(() => ac.abort());
+Use the close option to specify an array of event names that will end the iteration:
import { on, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
// Emit later on
process.nextTick(() => {
ee.emit('foo', 'bar');
ee.emit('foo', 42);
ee.emit('close');
});
for await (const event of on(ee, 'foo', { close: ['close'] })) {
console.log(event); // prints ['bar'] [42]
}
// the loop will exit after 'close' is emitted
console.log('done'); // prints 'done'
+Optionaloptions: StaticEventEmitterIteratorOptionsAn AsyncIterator that iterates eventName events emitted by the emitter
Optionaloptions: StaticEventEmitterIteratorOptionsStaticonceCreates a Promise that is fulfilled when the EventEmitter emits the given
+event or that is rejected if the EventEmitter emits 'error' while waiting.
The Promise will resolve with an array of all the arguments emitted to the
given event.
This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event
-semantics and does not listen to the 'error' event.
const { once, EventEmitter } = require('events');
async function run() {
const ee = new EventEmitter();
process.nextTick(() => {
ee.emit('myevent', 42);
});
const [value] = await once(ee, 'myevent');
console.log(value);
const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});
try {
await once(ee, 'myevent');
} catch (err) {
console.log('error happened', err);
}
}
run();
-The special handling of the 'error' event is only used when events.once()is used to wait for another event. If events.once() is used to wait for the
-'error' event itself, then it is treated as any other kind of event without
+
This method is intentionally generic and works with the web platform EventTarget interface, which has no special'error' event
+semantics and does not listen to the 'error' event.
import { once, EventEmitter } from 'node:events';
import process from 'node:process';
const ee = new EventEmitter();
process.nextTick(() => {
ee.emit('myevent', 42);
});
const [value] = await once(ee, 'myevent');
console.log(value);
const err = new Error('kaboom');
process.nextTick(() => {
ee.emit('error', err);
});
try {
await once(ee, 'myevent');
} catch (err) {
console.error('error happened', err);
}
+The special handling of the 'error' event is only used when events.once() is used to wait for another event. If events.once() is used to wait for the
+'error' event itself, then it is treated as any other kind of event without
special handling:
const { EventEmitter, once } = require('events');
const ee = new EventEmitter();
once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.log('error', err.message));
ee.emit('error', new Error('boom'));
// Prints: ok boom
-import { EventEmitter, once } from 'node:events';
const ee = new EventEmitter();
once(ee, 'error')
.then(([err]) => console.log('ok', err.message))
.catch((err) => console.error('error', err.message));
ee.emit('error', new Error('boom'));
// Prints: ok boom
+An AbortSignal can be used to cancel waiting for the event:
const { EventEmitter, once } = require('events');
const ee = new EventEmitter();
const ac = new AbortController();
async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}
foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
-Generated using TypeDoc
import { EventEmitter, once } from 'node:events';
const ee = new EventEmitter();
const ac = new AbortController();
async function foo(emitter, event, signal) {
try {
await once(emitter, event, { signal });
console.log('event emitted!');
} catch (error) {
if (error.name === 'AbortError') {
console.error('Waiting for the event was canceled!');
} else {
console.error('There was an error', error.message);
}
}
}
foo(ee, 'foo', ac.signal);
ac.abort(); // Abort waiting for the event
ee.emit('foo'); // Prints: Waiting for the event was canceled!
+Optionaloptions: StaticEventEmitterOptionsOptionaloptions: StaticEventEmitterOptionsStaticsetimport { setMaxListeners, EventEmitter } from 'node:events';
const target = new EventTarget();
const emitter = new EventEmitter();
setMaxListeners(5, target, emitter);
+Optionaln: numberA non-negative number. The maximum number of listeners per EventTarget event.
Rest...eventTargets: (EventTarget | EventEmitter<DefaultEventMap>)[]Different from Web GPIO API specification.
-Returns an iterable of entries in the map.
-Returns an iterable of key, value pairs for every entry in the map.
-Returns an iterable of keys in the map
-Returns an iterable of values in the map
-Generated using TypeDoc
Different from Web GPIO API specification.
+Optionalentries: null | readonly (readonly [number, GPIOPort])[]Optionaliterable: null | Iterable<readonly [number, GPIOPort], any, any>Readonly[toReadonlysizeStatic Readonly[species]Returns a specified element from the Map object. If the value that is associated to the provided key is an object, then you will get a reference to that object and any change made to that object will effectively modify it inside the Map.
+Returns the element associated with the specified key. If no element is associated with the specified key, undefined is returned.
+Adds a new element with a specified key and value to the Map. If an element with the same key already exists, the element will be updated.
+Staticgroup無効なアクセスエラー
-Creates an instance of InvalidAccessError.
-エラーメッセージ
-Optional override for formatting stack traces
-Create .stack property on a target object
-Generated using TypeDoc
無効なアクセスエラー
+Creates an instance of InvalidAccessError.
+エラーメッセージ
+操作エラー
-Creates an instance of OperationError.
-エラーメッセージ
-Optional override for formatting stack traces
-Create .stack property on a target object
-Generated using TypeDoc
操作エラー
+Creates an instance of OperationError.
+エラーメッセージ
+GPIO access with Node.js
+GPIO access with Node.js
+const { requestGPIOAccess } = require("node-web-gpio");
const { promisify } = require("util");
const sleep = promisify(setTimeout);
async function main() {
const gpioAccess = await requestGPIOAccess();
const port = gpioAccess.ports.get(26);
await port.export("out");
for (;;) {
await port.write(1);
await sleep(1000);
await port.write(0);
await sleep(1000);
}
}
main();
+const { requestGPIOAccess } = require("node-web-gpio");
const { promisify } = require("util");
const sleep = promisify(setTimeout);
async function main() {
const gpioAccess = await requestGPIOAccess();
const port = gpioAccess.ports.get(26);
await port.export("out");
for (;;) {
await port.write(1);
await sleep(1000);
await port.write(0);
await sleep(1000);
}
}
main();
-Generated using TypeDoc
Generated using TypeDoc
GPIO
-