Reducing Map: jQuery vs jQuery vs JavaScript | Hacker News Reader

Reducing Map: jQuery vs jQuery vs JavaScript

mrspeaker.net

36 pointsmrspeaker10 comments

Offtopic follows:

One thing that sucks about JS currently is the fact that you have to do Array.prototype.map.call(a, ...) instead of a.map, and even then you don't have a guarantee that the correct function will execute. I know in ECMAScript 5 you can freeze properties of an object, but unless prototypes of basic methods come frozen, it's not ideal.

Why exactly do you have to do that? Because some other unknown party could have overwritten the prototype with a new map function?

If that's the case, none of the basic objects are safe, not just Array..

Right. My point exactly. In most cases this is not a problem and sometimes can be really nice: like when you want to add some profiling code, etc. However, this is also pretty terrible when it comes to large code bases or when you see libraries out there that modify prototypes of base objects.

The post is a bit misleading. The "native" map method is only Javascript 1.6, so it isn't universally available.

"Reducing map: A short look at the similarities between the map functionality of jQuery 1.2+ inline map, jQuery 1.3.2 global map and JavaScipts 1.6+ native map function" didn't fit.

But if you're unfortunate enough to have to care about the ol' stuff, there are some nice polyfills on each of the MDC map/reduce/filter/etc pages: https://developer.mozilla.org/en/JavaScript/Reference/Global...

You can make it universally available with:

  if (!Array.prototype.map)
  {
	Array.prototype.map = function(fun /*, thisp */)
	{
	  "use strict";
  
	  if (this === void 0 || this === null)
		throw new TypeError();
  
	  var t = Object(this);
	  var len = t.length >>> 0;
	  if (typeof fun !== "function")
		throw new TypeError();
  
	  var res = new Array(len);
	  var thisp = arguments[1];
	  for (var i = 0; i < len; i++)
	  {
		if (i in t)
		  res[i] = fun.call(thisp, t[i], i, t);
	  }
  
	  return res;
	};
  }

I'm a big fan of es5-shim (https://github.com/kriskowal/es5-shim/), which monkey-patches these handy methods in older browsers.

I had no idea there were 3 different map options available.

Are you going to compare performance?

I personally use the map functioned defined in Underscore.js

Also check out the async library by caolan. Primarily designed for node.js, but also works with client-side. https://github.com/caolan/async

It's got the nice feature of providing synchronous and asynchronous maps, reduces, filters and everything else you'd expect.

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