What is variable scope?

Scope tells us about the visibility and accessibility of a variable. JavaScript has three scopes:

The global scope
Local scope

Block scope (ES6)

Global scope: Variables defined globally (i.e. not inside a block or function) are part of the global scope and can be accessed from anywhere in the code. When declared in the global scope, var, let and const behave the same in terms of scope.

var surname = 'Sharma';

The variable surname is global-scoped. It can be accessed anywhere in the script.

Local scope: Variables defined inside a block or function can only be accessed from the block or function where they were defined, as well as nested local scopes.

When declared inside a block scope, var will be available but undefined in outer scopes, while let and const will not exist in outer scopes.

var surname = 'Sharma';

function name() {
    var surname = 'Kumar';
    console.log(surname);
}

name();
console.log(surname);

Output-

Kumar
Sharma

When the JavaScript engine executes the name() function, it creates a function execution context.

And when the variable surname declared inside the name() function is bound to the function execution context of the function, not the global execution context.

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Learn Variable Scopes In JavaScript

What is variable scope?

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