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jeniabrook wants to merge 12 commits into from
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events: support EventTarget in once #29498

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c48786e
events: add support for EventTarget in once
jeniabrook Aug 18, 2019
0b69f8b
events: add test onceWithEventTarget
jeniabrook Aug 18, 2019
1a5f42d
events: add handling for error
jeniabrook Sep 3, 2019
ddd3efa
events: add more tests
jeniabrook Sep 3, 2019
9504593
events: update docs
jeniabrook Sep 8, 2019
3526b46
events: docs update
jeniabrook Sep 9, 2019
6f13b52
events: code review updates
jeniabrook Sep 10, 2019
646ae69
events: update test
jeniabrook Sep 10, 2019
b8d9389
events: remove redundant return
jeniabrook Sep 10, 2019
510270a
events: check first for EventTarget
jeniabrook Sep 11, 2019
126494c
Update doc/api/events.md
jeniabrook Sep 12, 2019
0cf3e5d
events: update tests
jeniabrook Sep 14, 2019
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events: add support for EventTarget in once
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@jeniabrook
jeniabrook committed Sep 12, 2019
commit c48786ea3f870c3ba3ab71655c919127898cf3d0
52 changes: 32 additions & 20 deletions lib/events.js
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Original file line number Diff line number Diff line change
Expand Up @@ -497,29 +497,41 @@ function unwrapListeners(arr) {

function once(emitter, name) {
return new Promise((resolve, reject) => {
const eventListener = (...args) => {
if (errorListener !== undefined) {
emitter.removeListener('error', errorListener);
}
resolve(args);
};
let errorListener;

// Adding an error listener is not optional because
// if an error is thrown on an event emitter we cannot
// guarantee that the actual event we are waiting will
// be fired. The result could be a silent way to create
// memory or file descriptor leaks, which is something
// we should avoid.
if (name !== 'error') {
errorListener = (err) => {
emitter.removeListener(name, eventListener);
reject(err);
if (emitter.addEventListener === undefined) {
const eventListener = (...args) => {
if (errorListener !== undefined) {
emitter.removeListener('error', errorListener);
}
resolve(args);
};
let errorListener;

// Adding an error listener is not optional because
// if an error is thrown on an event emitter we cannot
// guarantee that the actual event we are waiting will
// be fired. The result could be a silent way to create
// memory or file descriptor leaks, which is something
// we should avoid.
if (name !== 'error') {
errorListener = (err) => {
emitter.removeListener(name, eventListener);
reject(err);
};

emitter.once('error', errorListener);
}

emitter.once(name, eventListener);
return;
}

emitter.once('error', errorListener);
if (typeof emitter.addEventListener === 'function') {
// EventTarget does not have `error` event semantics like Node
// EventEmitters, we do not listen to `error` events here.
emitter.addEventListener(name, resolve, { once: true });
return;
}

emitter.once(name, eventListener);
throw new ERR_INVALID_ARG_TYPE('emitter', 'EventEmitter', emitter);
});
}