Variables scope in Javascript

Muhammad Bilal — Sun, 03 May 2020 13:40:04 +0000

Javascript variables are a container for storing values. In javascript, there are three types of variables let const and var.

var variable has a functional scope which means that variables that are defined inside a function can only be accessible within the function.

var type variables don't have block scope they are accessible outside of the block

var type variables override var type variable which has the same name in their scope.

Redeclaring a let or const variable with var is not allowed in the same scope and in functional scope

let type variable has the same functional scope as var variable but they also have Block sope

let type variable defined in Block are NOT accessible outside of Block as shown in the example.

Redeclaring a let variable with type let or const or var is not allowed in the global. The compiler will throw an error

Redeclaring a let variable with type let or const or var is not allowed in the block. The compiler will throw an error

Redeclaring a let variable with type let or const or var is not allowed in the functional scope. The compiler will throw an error

Now let's talk about const variables. As the name suggests we cannot reassign a value to the const variable.

const type variable also have functional and Block level scope.

const type variable defined in Block is NOT accessible outside of block as shown in the example.

Redeclaring a const variable with type let or const or var is not allowed in the global. The compiler will throw an error

Redeclaring a const variable with type let or const or var is not allowed in the block. The compiler will throw an error

Redeclaring a const variable with type let or const or var is not allowed in the functional scope. The compiler will throw an error

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