ES6 Declaration of Variables

There are three ways of declaration of variables using ‘var’, ‘let’, and ‘const’.

Var

• Variables declared with ‘var’ are function scoped they are accessible within the functions only.
• They are hoisted on the top of the scope.
• They can be re-defined and re-declared and can update the value.

var a = 10;

Let

• Variables declared with ‘let’ are block-scoped meaning they are accessible within the curly braces they are defined.
• They can not be hoisted on the top.
• They can not be re-declared and they can be updated.

let b= 30;

Const

• Variables declared with ‘const’ are block-scoped.
• They can not be reassigned.
• However Objects are arrays are declared with const for it; the properties and elements can be modified.

Const z = 50;

So, in ES6 there are total three ways to define variables in ES6 ‘var’, ‘let’ and ‘const’.