There are three types of scopes in JavaScript.

1. Global Scope
2. Function Scope
3. Block Scope

Global Scope

A variable declared outside a JavaScript function has a global scope. Such a variable is accessible by all functions and scripts on the page.

var language = "English";
// Variable 'language' is accessible here

function myFunction() {
  // Variable 'language' is accessible here
}

// Variable 'language' is accessible here

Function Scope

A variable declared inside a JavaScript function has a function scope. Such a variable is accessible only within the function and is considered to be local to that function.

// Variable 'language' is NOT accessible here

function myFunction() {
  var language = "English";
  // Variable 'language' is accessible here
}

// Variable 'language' is NOT accessible here

Block Scope

A variable declared inside a block { } has a block scope. Variables or constants declared with let or const keywords can have the block scope.

// eg. block scope
{
  let language = "English";
}
// Variable 'language' is NOT accessible here

Variables declared with var keyword cannot have block scope.

// eg. var
{
  var language = "English";
}
// Variable 'language' is accessible here