string concat vs array join

JavaScript performance comparison

Revision 3 of this test case created by Kyle Simpson

Info

Test the performance difference between string concact and array join for a large (10,000) number of words.

Preparation code

 
<script>
Benchmark.prototype.setup = function() {
    var words = ['this', 'is', 'a', 'test'];
   
    var text = words[0];
   
    var a = [words[0]];
   
    var i;
   
    var text2;
};
</script>

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Testing in unknown unknown
Test Ops/sec
Concat
for(i = 1; i < 10000; ++i)
{
    text += ' ' + words[i & 3] + Math.random();
}

text2 = text;
 
pending…
Join
for(i = 1; i < 10000; ++i)
{
    a.push(' ',words[i & 3],Math.random());
}

text2 = a.join('');
 
pending…

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1 comment

Quentin Barroin commented :

Hi Kyle,

I've just discovered your website today and i would like to know if you have some pdf supports about js performance ? I'm front-end developper and i would like product the best code according the best practices. :-) Thanks a lot in advance.

Kind regards,

Quentin.

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