events: use spread function param in emit
With recent changes in V8, it is now as performant or faster to use spread parameter within EventEmitter.prototype.emit, especially in cases where looping over arguments is required. events/ee-emit.js n=2000000 4.40 % *** 1.505543e-06 events/ee-emit-1-arg.js n=2000000 2.16 % *** 2.434584e-10 events/ee-emit-2-args.js n=2000000 1.05 % ** 0.001764852 events/ee-emit-3-args.js n=2000000 2.18 % *** 3.234954e-08 events/ee-emit-6-args.js n=2000000 17.17 % *** 1.298702e-103 events/ee-emit-10-args.js n=2000000 17.14 % *** 1.144958e-97 This has a knock-on effect for modules that use events extensively, such as http2: http2/headers.js nheaders=0 n=1000 2.10 % *** 6.792106e-11 PR-URL: https://github.com/nodejs/node/pull/16212 Reviewed-By: Luigi Pinca <luigipinca@gmail.com> Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de> Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Refael Ackermann <refack@gmail.com>
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@ -162,23 +162,22 @@ function emitMany(handler, isFn, self, args) {
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}
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}
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EventEmitter.prototype.emit = function emit(type) {
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var er, handler, len, args, i, events, domain;
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var needDomainExit = false;
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var doError = (type === 'error');
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EventEmitter.prototype.emit = function emit(type, ...args) {
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let doError = (type === 'error');
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events = this._events;
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const events = this._events;
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if (events !== undefined)
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doError = (doError && events.error === undefined);
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else if (!doError)
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return false;
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domain = this.domain;
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const domain = this.domain;
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// If there is no 'error' event listener then throw.
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if (doError) {
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if (arguments.length > 1)
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er = arguments[1];
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let er;
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if (args.length > 0)
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er = args[0];
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if (domain !== null && domain !== undefined) {
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if (!er) {
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const errors = lazyErrors();
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@ -202,37 +201,32 @@ EventEmitter.prototype.emit = function emit(type) {
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return false;
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}
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handler = events[type];
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const handler = events[type];
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if (handler === undefined)
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return false;
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let needDomainExit = false;
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if (domain !== null && domain !== undefined && this !== process) {
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domain.enter();
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needDomainExit = true;
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}
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var isFn = typeof handler === 'function';
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len = arguments.length;
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switch (len) {
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// fast cases
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case 1:
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const isFn = typeof handler === 'function';
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switch (args.length) {
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case 0:
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emitNone(handler, isFn, this);
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break;
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case 1:
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emitOne(handler, isFn, this, args[0]);
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break;
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case 2:
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emitOne(handler, isFn, this, arguments[1]);
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emitTwo(handler, isFn, this, args[0], args[1]);
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break;
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case 3:
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emitTwo(handler, isFn, this, arguments[1], arguments[2]);
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emitThree(handler, isFn, this, args[0], args[1], args[2]);
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break;
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case 4:
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emitThree(handler, isFn, this, arguments[1], arguments[2], arguments[3]);
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break;
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// slower
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default:
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args = new Array(len - 1);
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for (i = 1; i < len; i++)
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args[i - 1] = arguments[i];
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emitMany(handler, isFn, this, args);
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}
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