Array map

[millermedeiros]

changed some of the loops to Array.map().

[wjcrowcroft]

I was just checking out _.map in underscore.js:

  // Return the results of applying the iterator to each element.
  // Delegates to **ECMAScript 5**'s native `map` if available.
  _.map = function(obj, iterator, context) {
    var results = [];
    if (obj == null) return results;
    if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);
    each(obj, function(value, index, list) {
      results[results.length] = iterator.call(context, value, index, list);
    });
    return results;
  };

Compare to the new map method in accounting.js which achieves pretty much the same goal:

    function map(arr, fn, thisVal){
        var i = 0,
            n = arr.length,
            result = [];
        while(i < n){
            result[i] = fn.call(thisVal, arr[i], i, arr);
            i += 1;
        }
        return result;
    }

Maybe we can merge them - obviously underscore has its own each method to use, this one could stick to a fallback loop like above... Maybe something like this would work?:

    var nativeMap = Array.prototype.map; // earlier

    function map(obj, iterator, context){
        var results = [];
        if (obj == null) return results;

        // Use native .map method if it exists:
        if (nativeMap && obj.map === nativeMap) return obj.map(iterator, context);

        // Fallback for native .map:
        for (var i = 0; i < obj.length; i++ ) {
            results[i] = iterator.call(context, obj[i], i, obj);
        }
        return results;
    }

Just put that together in the comment and haven't actually tested it - I'll play around with it in the console now.. let me know if you see any issues.

[millermedeiros]

this will work and will be faster on modern browsers, didn't implemented like this for brevity, I would also cache the array length. see jsperf test

[wjcrowcroft]

Yeah, it looks great. Thanks for doing the jsperf test.

Want to commit the changes to this branch, so I can auto-merge it? Or I can merge these into dev and change it myself, if you don't have time, no problem.

[wjcrowcroft]

I've committed these to the dev branch, along with the changes we proposed. Thanks!