ES6 block level scope and new variable declaration (let) __javascript

Many languages have block-level scopes, but JS does not, it uses VAR to declare variables, function to divide the scope, curly braces "{}" can not limit the scope of var. Variables declared with VAR have the effect of variable elevation (declaration hoisting).

ES6 adds a let, which can be declared in {}, if, for. The usage is the same as Var, but the scope is scoped to the block level, and there is no variable elevation for the variable of let declaration.

Example 1: block level scope if

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function Getval (boo) {if (boo) {var val = ' red '//... return val} else { Here you can access Val return null}