Fastest array loops in Javascript (v236)

Revision 236 of this benchmark created by ome on

Preparation HTML

<script>
  function someFn(ix) {
    try { 
        ix += 1; 
        if (ix < 0) {
           throw new Error('e');
        }
    } catch (e){
        alert(e);
    }
    return ix * 5 + 1 / 3 * 8;
  }
</script>

Setup

// Populate the base array
    var arr = [],
      a, i, len, arr2 = [];
    for (i = 0; i < 1000; i++) {
      arr[i] = i + 1;
    }

Test runner

Ready to run.

Testing in
TestOps/sec
For loop, basic
for (i = 0; i < arr.length; i++) {
  someFn(arr[i]);
}
ready
While loop, basic
i = 0;
while (i != arr.length) {
  someFn(arr[i++]);
}
ready
For loop, cached
for (i = 0, len = arr.length; i < len; i++) {
  someFn(arr[i]);
}
ready
For loop, i--
for (i = arr.length; i > 0; i--) {
  someFn(arr[i]);
}
ready
Do-while loop, i--
i = arr.length - 1;
do {
  someFn(arr[i]);
}
while (i--);
ready
Do-while loop, --i
i = arr.length;
if (i > 0) {
  do {
    someFn(arr[i]);
  }
  while (--i);
}
ready
For..in loop
for (var i in arr) {
  someFn(arr[i]);
}
ready
forEach
arr.forEach(function(v) {
  someFn(v)
})
ready
While ! Undefined
i = 0;
while ((a = arr[i++]) !== undefined) {
  someFn(a);
}
ready
Order w/ array copy
arr2 = [];
while (i = arr.shift()) {
  someFn(i);
  arr2.push(i);
}
arr = arr2;
ready
While length--
i = arr.length;
while (i--) {
  someFn(arr[i]);
}
ready
Pop w/ copy
arr2 = [];
while (i = arr.pop()) {
  someFn(i);
  arr2.push(i);
}
arr = arr2;
ready
shift()
while (i = arr.shift()) {
  someFn(i);
}
ready
Forloop ! Null
for (var i = 0, item;
  (item = arr[i]) != null; i++) {
  someFn(item);
}
ready
Reverse For-loop
for (var i = arr.length; --i;) {
  someFn(arr[i]);
}
ready

Revisions

You can edit these tests or add more tests to this page by appending /edit to the URL.