PowerArray

Turns out that you can re-write some of the methods of Array to obtain a much better performance than the native methods. In particular, Array.forEach seems to perform pretty badly.

Note: the overridden methods of PowerArray break compliance, the focus is on performance so take a look at the caveat section below.

It looks as if a for loop with cached length is the fastest way of iterating.

var i, len = array.length;
for (i = 0; i < len; i += 1) {
  someFun(array[i]);
}

So I rewrote the Array class as PowerArray and implemented the above mechanism in PowerArray.forEach with surprising results.

The results are as follows: PowerArray.forEach is averagely 5 times faster than native Array.

This is only a proof of concept.

Install with npm install powerarray

Proposed Usage

Particularly useful for arrays that need processing on all elements often, or for numeric arrays utilized as indexes for Collections of data.

Methods

All Array native methods are available through PowerArray. The following methods are either extending or overriding the native Array class.

PowerArray.forEach: utilizes a for loop for iteration, takes a callback which receives an element and the index of that element.

PowerArray.map: utilizes a for loop to return a PowerArray of mapped values, takes a callback processing function argument.

PowerArray.binarySearch: performs a binary search on the elements of the array, only relevant if the array only consists of numbers. Thanks to Oliver Caldwell's post for a quick version of the algorithm. Also note the contribution of Yehonatan and other authors of comments to the post which helped to optimise the implementation of binary search further.

PowerArray.numericSort: sorts array (if array only contains integers), useful for utilizing binarySearch. Optional sorting function argument.

PowerArray.addAndSort: adds a new value and sorts the array automatically

Contribution

Pull requests are more than welcome, just make sure to add a test in tests/test.js (and that it passes it obviously).

Caveats

Thanks to David Souther for documenting these:

1. No this context in fn calls, handle your own binding.
2. No determination if i is a member of PowerArray (eg for sparse arrays, [2, 4, , 6])
3. No exception is thrown when the callback isn't callable.

There may be more, please feel free to flag those or include them yourself through a pull request.