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events: unwrap #once listeners in #listeners #6881

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events: unwrap #once listeners in #listeners #6881

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12 changes: 10 additions & 2 deletions lib/events.js
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Original file line number Diff line number Diff line change
Expand Up @@ -425,9 +425,9 @@ EventEmitter.prototype.listeners = function listeners(type) {
if (!evlistener)
ret = [];
else if (typeof evlistener === 'function')
ret = [evlistener];
ret = [evlistener.listener || evlistener];
else
ret = arrayClone(evlistener, evlistener.length);
ret = unwrapListeners(evlistener);
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@yorkie yorkie Aug 6, 2016 •
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Should we remove the arrayClone function and do replace all arrayClone() to unwrapListeners()?

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No, the other usages of arrayClone expect the wrapped listeners.

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@yorkie yorkie Aug 6, 2016 •
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However I think the only difference between is that arrayClone supports a copy with a specified length, 2nd argument and the assignment from .listener of elements.

The function upwrapListeners seems to be only used inside to EE.prototype.listeners, so could we declare this function inside the prototype method to be unwrap? Both the functions defined at bottom looks like those pure collection ones.

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I would expect declaring unwrapListeners within listeners (I believe that's what you're suggesting?) to result in a performance degradation.

}

return ret;
Expand Down Expand Up @@ -475,3 +475,11 @@ function arrayClone(arr, i) {
copy[i] = arr[i];
return copy;
}

function unwrapListeners(arr) {
const ret = new Array(arr.length);
for (var i = 0; i < ret.length; ++i) {
ret[i] = arr[i].listener || arr[i];
}
return ret;
}
13 changes: 13 additions & 0 deletions test/parallel/test-event-emitter-listeners.js
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Expand Up @@ -36,3 +36,16 @@ function listener2() {}
assert.deepStrictEqual(ee.listeners('foo'), [listener, listener2]);
assert.deepStrictEqual(eeListenersCopy, [listener]);
}

{
const ee = new events.EventEmitter();
ee.once('foo', listener);
assert.deepStrictEqual(ee.listeners('foo'), [listener]);
}

{
const ee = new events.EventEmitter();
ee.on('foo', listener);
ee.once('foo', listener2);
assert.deepStrictEqual(ee.listeners('foo'), [listener, listener2]);
}