Does declaring variables in a loop waste memory?

Asked May 12 '16 at 12:37

Active May 12 '16 at 12:45

Viewed 156 times

Consider this:

var i = 0;
var isEight = false;

while(true){
    if( i === 8) {
        isEight = true;
        break;
    }
    i++;
}

versus this:

var i = 0;

while(true){
    var isEight = false; // moved declaration inside 
    if( i === 8) {
        isEight = true;
        break;
    }
    i++;
}

The example is contrived but you get the idea. How does Javascript respond when the declaration of isEight is brought inside the loop?

Does a new memory space get allocated every time that line runs? Will this be a serious issue if the loop runs many many times?

Update: Since alex pointed out, what about using let instead of var in this case.

edited May 12 '16 at 12:45

asked May 12 '16 at 12:37

Cheng

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`isOdd` should be `isEight` right? – TryingToImprove May 12 '16 at 12:39
@TryingToImprove yes, thanks for pointing it out – Cheng May 12 '16 at 12:40
3

The declaration is hoisted so it's unlikely that there's any practical difference. In any case it would depend on the JS engine. – JJJ May 12 '16 at 12:40
3

It would be a more interesting question if you were using `let` there instead of `var`. – alex May 12 '16 at 12:41
Declaration of variable is done first anyway in Javascript so I believe they're not declared again if you put them in a loop? – Strah Behry May 12 '16 at 12:42
`let` is *designed* for use cases like this, so it would be highly unlikely that JS engines wouldn't know how to manage memory correctly. – JJJ May 12 '16 at 12:52

Does declaring variables in a loop waste memory?

0 Answers0