Remove Array.prototype.slice for arguments for optimization

[arusakov]

Hi, thanks for great websocket library!

There are some good topics about optimizations, for example: Optimization-killers. Functions with Array.prototype.slice.call(arguments) cannot be optimized. So I replaced them like this commit in Node.js from one of V8 developer.

[arusakov]

@brycekahle I do not understand what is wrong with the tests :(

[brycekahle]

The tests were failing before, so likely not because of your code changes.

[3rd-Eden]

instead of doing args = [] it would be better to just allocate an array with the size of the arguments, and adding adding the arguments to the correct index.

[arusakov]

new Array(arguments.length) is the best solution for browsers based on latest version of V8 (Chrome, Opera, etc), but for some browsers (old IE8, IE9, old V8 based browsers, maybe Firefox - I'm not sure now) args = [] and args.push() is faster. So I think, args = [] - is good, is middle way - newest browsers are fast, older browsers - work as quickly as possible

[arusakov]

@3rd-Eden I write some test, put it in project root folder and run with node (I use v4.1.1):

var Emitter = require('./lib/event/emitter').EventEmitter;

function test() {
  var emitter = new Emitter();
  var COUNT = 1e5;

  var forTest = 0;

  // add two listeners
  emitter.on('message', function (data) {
    forTest += data.val;
  });
  emitter.on('message', function (data) {
    forTest -= data.val;
  });

  // random value
  var rndSeed = Date.now() % 10;

  var t1 = Date.now();
  for (var i = 0; i < COUNT; ++i, ++rndSeed) {
    emitter.emit('message', {
      val: rndSeed
    });
  }
  t1 = Date.now() - t1;
  console.log(t1, forTest);
}

test();

I got the following results (less time - better):

Version	time (ms)
slice	130
[] and push	25

[richotaylor]

Just ran into this as well. Would love to see it be merged.

[lpinca]

The solution proposed by @3rd-Eden is indeed faster even in IE8. You can test it here http://jsperf.com/arguments-push-vs-nopushcall