Fastest array loops in Javascript (v170)

Revision 170 of this benchmark created on

Preparation HTML

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

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

Test runner

Ready to run.

Testing in
TestOps/sec
For loop, basic
for (var i = 0; i < arr.length; i++) {
  someFn(arr[i]);
}
ready
While loop, basic
var i = 0;
while (i < arr.length) {
  someFn(arr[i]);
  i++;
}
ready
For loop, cached
for (var i = 0, len = arr.length; i < len; i++) {
  someFn(arr[i]);
}
ready
For loop, i--
for (var i = arr.length; i > 0; i--) {
  someFn(arr[i]);
}
ready
Do-while loop, i--
var i = arr.length - 1;
do {
  someFn(arr[i]);
}
while (i--);
ready
Do-while loop, --i
var 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
Order
var i;
while (i = arr.shift()) {
  someFn(i);
}
ready
forEach
arr.forEach(function(v) {
  someFn(v)
})
ready
order validation
var i;
while ((i = arr.shift()) !== undefined) {
  someFn(i);
}
ready
While ! Undefined
var a, i = 0;
while ((a = arr[i++]) !== undefined) {
  someFn(a);
}
ready
Pop
var i;
while (i = arr.pop()) {
  someFn(i);
}
ready
Order w/ array copy
var i, copy = arr.slice(0);
while (i = copy.shift()) {
  someFn(i);
}
ready
copy reverse pop
var i, arr2 = arr.slice().reverse();
while (i = arr2.pop()) {
  someFn(i);
}
ready
While ! Undefined (array end + &&)
var a, i = 0,
  len = arr.length;
while (i !== len) {
  ((a = arr[i++]) !== undefined) && someFn(a);
}
ready
While ! Undefined (array end)
var i = 0,
  len = arr.length;
while (i !== len) {
  someFn(arr[i++]);
}
ready
Generated + eval
var i = 0,
  len = arr.length,
  body = "",
  f = someFn,
  a = arr;
while (i !== len) {
  body += "f(a[" + i + "]);";
}
eval(body);
ready
While reverse
var i = arr.length;
while (i--) {
  someFn(arr[i]);
}
ready
For loop, cached #2
var i = 0,
  l = arr.length;
for (; i < l; i++) {
  someFn(arr[i]);
}
ready
for loop, inversed cached
var l = arr.length;
for (; l !== 0;) {
  someFn(arr[--l]);
}
ready

Revisions

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