Sample Analysis of not using for-in on arrays in JavaScript

This article mainly introduces the JavaScript do not use for-in on the array of example analysis, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let Xiaobian with you to understand.

Do not use for-in on arrays

Avoid:

Var sum = 0; for (var i in arrayNumbers) {sum + = arrayNumbers [I];} / / Welcome to join the front-end full-stack development communication circle to learn and communicate together: 1007317281

Even better:

Var sum = 0; for (var I = 0, len = arrayNumbers.length; I < len; iTunes +) {sum + = arrayNumbers [I];} / / Welcome to join the front-end full stack development communication circle to learn and communicate together: 1007317281

Another benefit is that the I and len variables are in the first declaration of the for loop, and they are initialized only once, which is faster than the following:

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