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lyle/arrayLengthTest.js

Created May 13, 2013 22:14
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Testing speed on Arrays in JS client side - I was curious if calling instanceOfArray.length was slower then referencing an intager.
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arrayLengthTest.js
var smallArray = 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function lengthPer(inArray){
var i=0;
for(i=0;i<inArray.length;i++){
}
return i;
}
function lengthOnce(inArray){
var i=0;
var leng = inArray.length;
for(i=0;i<leng;i++){
}
return i;
}
Raw
testArray.html
<html>
<head>
<title>Testing Array Length Access Speed</title>
<script type="text/javascript" src="arrayLengthTest.js"></script>
</head>
<body>
<div id="out"></div>
<button id="doIt">Do It</button>
<script type="text/javascript">
document.getElementById('doIt').addEventListener('click',function(){testSpeed();},false);
function testSpeed() {
var parent=0;
var start1, end1, start2, end2;
start1 = Date.now();
for(parent=0;parent<1000000;parent++){
lengthPer(smallArray);
}
end1 = Date.now();
start2 = Date.now();
for(parent=0;parent<1000000;parent++){
lengthOnce(smallArray);
}
end2 = Date.now();
alert("length called each loop=" + (end1 - start1) + "\nlength called once=" + (end2 - start2) );
}
</script>
</body>
</html>
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