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A couple questions:

  1. Is a regular javascript loop (to loop through a series of elements) faster/more efficient than using jQuery each() ??

  2. If so, what is the best way to write the following code as a regular javascript loop?

$('div').each(function(){ //... })

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If you're really interested in loop efficiency, have a look here. stackoverflow.com/questions/1340589/… – James Montagne Aug 24 '12 at 21:51
1  
A for loop is faster, but note that if what you're doing within the loop involves callback functions that need to use the loop index variable later then you would need to introduce a closure and that would (more or less) cancel out the efficiency gains. – nnnnnn Aug 24 '12 at 21:54

2 Answers

up vote 5 down vote accepted

Yes, removing the each() will give you slightly better performance. This is how you could write a for loop for a list of elements.

var divs = $('div');

for(var i = 0; i < divs.length; i++){
    var thisDiv = divs[i]; // element

    var $thisDiv = $(divs[i]); // jquery object

    // do stuff
}
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To answer the first part of the question, yes a regular loop is going to be slightly more efficient due to the removal of some overhead. The difference should be very small. – James Montagne Aug 24 '12 at 21:44
And this: jsperf.com/for-vs-foreach-vs-each/24 – Jason Sperske Aug 24 '12 at 21:47
1  
divs[i] is not a jquery object. You would have to $(divs[i]) – Gabe Aug 24 '12 at 21:49
1  
brilliant, Gabe, thanks so much. – j-man86 Aug 24 '12 at 21:49
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up vote 2 down vote 
var divs = document.getElementsByTagName('div'),
    l = divs.length, i, cur;

for(i=0; i<l; i++) {
    cur = divs[i];
    // do stuff with cur here
}

Please continue on your path to removing jQuery in the name of efficiency. This code is approximately fifty times faster than the jQuery equivalent.

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4  
It's only 50x faster if you have nothing in the "do stuff with cur here" part. It's faster, but the 50x is misleading in the grand scheme. – James Montagne Aug 24 '12 at 21:45

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