Does avoiding individual variables speed up JavaScript performance?

Question

It is common in JavaScript to avoid unnecessary variables, as it reduces the size of JS codes, though readability of defining individual variables is better. In a simple example,

var e=document.getElementById('text');
var text=e.innerHTML;
var d=document.getElementById('test');
d.innerHTML=text;

this can be reduced to

document.getElementById('test').innerHTML=document.getElementById('text').innerHTML;

I wonder if this has any benefit from performance point of view. Does avoiding excess variables reduce memory usage and enhance process speed?

Is it a serious issue? and it is always recommended to minimize the JS code by avoiding individual variables?

Is it a serious issue? No. If you do it only because of "performance" you're micro-optimizing. — JJJ
– JJJ, Commented Sep 22, 2013 at 5:36
In the example you've given, there really is not much need to - the latter is perfectly readable. Do what is most readable though, unless it comes down to some core function that is called hundreds of times per second. In that case, look for the biggest gains first - it probably won't be here. — Qantas 94 Heavy
– Qantas 94 Heavy, Commented Sep 22, 2013 at 5:42

user149341 · Accepted Answer · 2013-09-22 05:48:16Z

1

There is no practical difference between the two. Most Javascript interpreters are likely to generate an equivalent internal representation for both, and the overhead of the functions and properties you're using in this example (particularly assigning to innerHTML!) is vastly greater than any difference you'd be likely to see.

answered Sep 22, 2013 at 5:48

user149341

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1 Comment

Raymond Chen Over a year ago

My only concern is that the variables might be unwittingly captured by a long-lived closure (creating a leak), depending on how good the JavaScript interpreter is.

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