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<!doctype html>
<html lang="en">
<head>
<title>JavaScript Patterns</title>
<meta charset="utf-8">
</head>
<body>
<script>
/* Title: for loops
* Description: optimized for loops
*/
// sub-optimal loop
for (var i = 0; i < myarray.length; i++) {
// do something with myarray[i]
}
// optimization 1 - cache the length of the array with the use of `max`
for (var i = 0, max = myarray.length; i < max; i++) {
// do something with myarray[i]
}
// optimization 2 - use single var pattern for consistency
// NOTE: A drawback is that it makes it a little harder to copy and paste whole loops while refactoring code.
var i = 0,
max,
myarray = [];
for (i = 0, max = myarray.length; i < max; i++) {
// do something with myarray[i]
}
// optimization 3 - substitute `i++` with `i = i + 1` or `i += 1` to avoid excessive trickiness
var i = 0,
max,
myarray = [];
for (i = 0, max = myarray.length; i < max; i += 1) {
// do something with myarray[i]
}
// preferred 1
var i, myarray = [];
for (i = myarray.length; i--;) {
// do something with myarray[i]
}
// preferred 2
var myarray = [],
i = myarray.length;
while (i--) {
// do something with myarray[i]
}
// References
// http://net.tutsplus.com/tutorials/javascript-ajax/the-essentials-of-writing-high-quality-javascript/
</script>
</body>
</html>