For Loop vs. Optimized For Loop

JavaScript performance comparison

Revision 17 of this test case created by Josh

Info

A speed comparison between for loops.

Preparation code

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Preparation code output

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Testing in unknown unknown
Test Ops/sec
Customary For Loop
 
var anchors = document.getElementsByTagName("a");

for (i = 0; i < anchors.length; i++) {
  anchors[i].style.color = "red";
}
 pending…
Optimized For Loop
 
var anchors = document.getElementsByTagName("a");

for (var i = anchors.length - 1; i >= 0; i -= 1) {
  anchors[i].style.color = "red";
}
 pending…
Optimized While Loop
 
var anchors = document.getElementsByTagName("a"),
    i = anchors.length;

while (i--) {
  anchors[i].style.color = "red";
}
 pending…
Optimize Do While Loop
 
var anchors = document.getElementsByTagName("a"),
    i = anchors.length - 1;

do {
  anchors[i].style.color = "red";
}
while (i--);
 pending…

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