fast-array-filter

JavaScript performance comparison

Test case created by John-David Dalton

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 array = [];
    array[200] = 'a';
   
    function callback(v) {
      return /\w+/.test(v);
    }
};
</script>

Test runner

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Testing in unknown unknown
Test Ops/sec
native
array.filter(callback);
pending…
custom
array.filter2(callback);
pending…

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2 comments

John-David Dalton (revision owner) commented :

So Opera 12.00 is like whoa!? :D

fearphage commented :

Opera Mobile beat the desktops on native.

var me = 'impressed';

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