fast-array-filter

JavaScript performance comparison

Revision 4 of this test case created

Info

This is an Array#filter implementation from a recent 140bytes code golf entry. It's faster than native Array#filter when iterating over large sparse arrays because it doesn't use the length property to calculate when it should stop iterating.

Preparation code

<script>
Array.prototype.filter2 = function(
  a, //a function to test each value of the array against. Truthy values will be put into the new array and falsey values will be excluded from the new array
  b, // placeholder
  c, // placeholder
  d, // placeholder
  e // placeholder
) {
  c = this; // cache the array
  d = []; // array to hold the new values which match the expression
  for (e in c) // for each value in the array,
    ~~e + '' == e && e >= 0 && // coerce the array position and if valid,
    a.call(b, c[e], +e, c) && // pass the current value into the expression and if truthy,
    d.push(c[e]); // add it to the new array
 
  return d // give back the new array
};
</script>
<script>
Benchmark.prototype.setup = function() {
    var sparse_array = []
    sparse_array[200] = 'a'
   
    var dense_array = [];
    for(var i=0; i<200; i++) {
      dense_array[i] = String.fromCharCode(Math.round(Math.random() * 95 + 33))
    }
   
   
    function callback(v) {
      return /\w+/.test(v);
    }
};
</script>

Test runner

Warning! For accurate results, please disable Firebug before running the tests. (Why?)

Java applet disabled.

Testing in unknown unknown
Test Ops/sec
native vs sparse array
sparse_array.filter(callback);
pending…
custom vs sparse array
sparse_array.filter2(callback);
pending…
native vs dense array
dense_array.filter(callback);
pending…
custom vs dense array
dense_array.filter2(callback);
pending…

Compare results of other browsers

Revisions

You can edit these tests or add even more tests to this page by appending /edit to the URL. Here’s a list of current revisions for this page:

0 comments

Add a comment