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events: improve once() performance

PR-URL: #29307
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Yongsheng Zhang <zyszys98@gmail.com>
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mscdex authored and BridgeAR committed Aug 25, 2019
1 parent 6a914ed commit 3bc16f917d9f3416815c941cae04790020be469e
Showing with 48 additions and 10 deletions.
  1. +44 −8 benchmark/events/ee-once.js
  2. +4 −2 lib/events.js
@@ -2,18 +2,54 @@
const common = require('../common.js');
const EventEmitter = require('events').EventEmitter;

const bench = common.createBenchmark(main, { n: [2e7] });
const bench = common.createBenchmark(main, {
n: [2e7],
argc: [0, 1, 4, 5]
});

function main({ n }) {
function main({ n, argc }) {
const ee = new EventEmitter();

function listener() {}

bench.start();
for (var i = 0; i < n; i += 1) {
const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
ee.once(dummy, listener);
ee.emit(dummy);
switch (argc) {
case 0:
bench.start();
for (let i = 0; i < n; i += 1) {
const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
ee.once(dummy, listener);
ee.emit(dummy);
}
bench.end(n);
break;
case 1:
bench.start();
for (let i = 0; i < n; i += 1) {
const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
ee.once(dummy, listener);
ee.emit(dummy, n);
}
bench.end(n);
break;
case 4:
bench.start();
for (let i = 0; i < n; i += 1) {
const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
ee.once(dummy, listener);
ee.emit(dummy, 'foo', argc, 'bar', false);
}
bench.end(n);
break;
case 5:
bench.start();
for (let i = 0; i < n; i += 1) {
const dummy = (i % 2 === 0) ? 'dummy0' : 'dummy1';
ee.once(dummy, listener);
ee.emit(dummy, true, 7.5, 'foo', null, n);
}
bench.end(n);
break;
default:
throw new Error('Unsupported argument count');
}
bench.end(n);
}
@@ -290,11 +290,13 @@ EventEmitter.prototype.prependListener =
return _addListener(this, type, listener, true);
};

function onceWrapper(...args) {
function onceWrapper() {
if (!this.fired) {
this.target.removeListener(this.type, this.wrapFn);
this.fired = true;
return Reflect.apply(this.listener, this.target, args);
if (arguments.length === 0)
return this.listener.call(this.target);
return this.listener.apply(this.target, arguments);
}
}

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