Fastest array loops in Javascript

JavaScript performance comparison

Revision 182 of this test case created by

Preparation code

<script>
  // Populate the base array
  var arr = [];
  for (var i = 0; i < 1000; i++) {
    arr[i] = 'value' + i;
  }

  function someFn(ix) {
    return ix * 5 + 1 / 3 * 8;
  }

var len = arr.length
  , i = 0;
</script>
    

Test runner

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
For loop, basic
for (var i = 0; i < arr.length; i++) {
  someFn(i);
}
pending…
While loop, basic
var i = 0;
while (i < arr.length) {
  someFn(i);
  i++;
}
pending…
For loop, cached
for (var i = 0, len = arr.length; i < len; i++) {
  someFn(i);
}
pending…
For loop, i--
for (var i = arr.length; i > 0; i--) {
  someFn(i);
}
pending…
Do-while loop, i--
var i = arr.length - 1;
do {
  someFn(i);
}
while (i--);
pending…
Do-while loop, --i
var i = arr.length;
if (i > 0) {
  do {
    someFn(i);
  }
  while (--i);
}
pending…
For..in loop
for (var i in arr) {
  someFn(i);
}
pending…
while loop i--
var i = arr.length;
while (i--) {
  someFn(i);
}
pending…
For loop, i -= 1
for (var i = arr.length; i > 0; i -= 1) {
  someFn(i);
}
pending…
For loop, i -= 1 II
var i;
for (i = arr.length; i > 0; i -= 1) {
  someFn(i);
}
pending…
For loop
var i;
for (i = arr.length; i > 0; i--) {
  someFn(i);
}
pending…
Fast
for (; i < len; ++i) {
  someFn(i);
}
pending…
Fastest?
var i = 0;
for (; i !== len; ++i) {
  someFn(i);
}
pending…
test another
var i = 0;
for (; i !== len; --i) {
  someFn(i);
}
pending…
another
var i = 0;
for (; i !== len; i-=1) {
  someFn(i);
}
pending…
another i+= 1
var i = 0;
for (; i !== len; i+=1) {
  someFn(i);
}
pending…
another test
pending…
another
var i = 0;
for (; i!len; --i) {
  someFn(i);
}
pending…
For (cached) ++i
for (var i = 0, len = arr.length; i < len; ++i) {
  someFn(i);
}
pending…

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