Difference between ES6 and ES5

1. ES6 added a let command to declare a variable. It is used in a similar way var , but the declared variable is let valid only within the code block where the command resides.

    {        var a = 1;         = 1;    }    A;    b;/

Let does not have variable promotion like Var , that is, variables must be declared before they can be used

2, block-level scope

ES5 only global scope and function scope, no block-level scope

Difference between ES6 and ES5