Loops

JavaScript performance comparison

Revision 116 of this test case created by

Preparation code 

<script>
  var arr = new Array(100);
  var obj = {length: 100};
  var ii = 0;
  for(; ii < obj.length; ++ii) { obj[ii] = null }
</script>

Preparation code output

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Testing in CCBot 2.0.0 / Other 0.0.0
Test Ops/sec
while loop that imitates a for loop 
var i = 0;
while (i < arr.length) {
 arr[i];
 i++;
};
 pending…
while loop that imitates a for loop, caching the length 
var i = 0,
    len = arr.length;
while (i < len) {
 arr[i];
 i++;
};
 pending…
Reverse while loop 
var i = arr.length;
while (i--) {
 arr[i];
};
 pending…
Reverse while loop without implicit ToBoolean 
var i = arr.length;
while (i-- > 0) {
 arr[i];
};
 pending…
Reverse do … while loop 
var i = arr.length;
do {
 arr[i];
} while (i--);
 pending…
Reverse for loop 
for (var i = arr.length; i--;) {
 arr[i];
};
 pending…
Old ’n’ busted for loop 
for (var i = 0; i < arr.length; ++i) {
 arr[i];
};
 pending…
Old ’n’ busted for loop, caching the length 
for (var i = 0, len = arr.length; i < len; ++i) {
 arr[i];
};
 pending…
Cool guy loop 
for (var i = -1; ++i < arr.length;) {
 arr[i];
};
 pending…
Cool guy loop, caching the length 
for (var i = -1, len = arr.length; ++i < len;) {
 arr[i];
};
 pending…
Native Array#forEach implementation 
arr.forEach(function(x) {
 x;
});
 pending…
Native Array#forEach implementation with named function 
function foo(x) {
 x;
};
arr.forEach(foo);
 pending…
Old 'n' busted with object mimicking array 
for (var i = 0; i < obj.length; ++i) {
 obj[i];
};
 pending…
Old 'n' busted with object mimicking array and cached length 
var obj_length = obj.length;
for (var i = 0; i < obj_length; ++i) {
 obj[i];
};
 pending…

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Revisions

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