How to declare variables with the keyword let in es6

Editor to share with you how to use the keyword let to declare variables in es6, I believe most people do not know much about it, so share this article for your reference, I hope you can learn a lot after reading this article, let's go to know it!

Declare variables with the keyword let

Let a; / / undefinedlet b = 1; function add (b) {let sum = b + 1; return sum;} let c = add (b)

"javascript strict mode" is required: 'use strict'

There is no variable promotion.

Repetition is not allowed.

The variable scope declared by let is in the block-level domain. After using let definition inside the function, it has no effect on the outside of the function (block-level scope).

You can assign a value to a variable when you declare it, with a default value of undefined, or you can assign a value to the variable later in the script, which cannot be used before life (temporary dead zone)

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