Block scope

ES6 provides additional scope while declaring variables. We looked at function scope and how it affects variables declared with the var keyword. If you are coding in ES6, block scope will mostly replace your need to use variables declared using var. Although, if you are still with ES5, we want you to make sure that you look at hoisting behavior carefully.

ES6 introduces the let and const keywords that allow us to declare variables.

Variables declared with let are block-scoped. They exist only within the current block. Variables declared with var are function scoped, as we saw earlier. The following example illustrates the block scope:

    var a = 1; 
    { 
        let a = 2; 
        console.log( a );   // 2 
    } 
    console.log( a );       // 1 

The scope between an opening brace'{' and a closing brace '}' is a block. If you are coming from a background in Java or C/C++, the concept of a block scope will be very familiar to you. In those languages...