How JavaScript avoids using for-in to traverse an array

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Avoid using for-in to traverse an array

Avoid using this approach:

Var sum = 0 for (var i in arrayNumbers) {sum + = arrayNumbers [I];}

A better way is:

Var sum = 0 for (var I = 0, len = arrayNumbers.length; I < len; iTunes +) {sum + = arrayNumbers [I];}

As an added bonus, the values of both the I and len variables are executed only once

Will be more efficient than the following:

For (var I = 0; I < arrayNumbers.length; iTunes +)

Why? Because arrayNumbers.length is counted every time it loops.

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