Interview question

What is scope and the scope chain in JavaScript? JavaScript में scope और scope chain क्या है?

Answer

Scope determines the accessibility of variables. JavaScript has global scope, function scope, and block scope (with let/const).

// Global scope
let global = 'I am global';

function outer() {
    let outerVar = 'outer';
    
    function inner() {
        let innerVar = 'inner';
        console.log(innerVar);   // 'inner' - own scope
        console.log(outerVar);   // 'outer' - parent scope
        console.log(global);     // 'I am global' - global scope
    }
    inner();
}
outer();

Scope Type	Description
Global scope	Variables accessible everywhere
Function scope	Variables accessible only within the function
Block scope	Variables (let/const) accessible only within the block (if, for, etc.)
Scope chain	JavaScript looks up variable in local scope, then parent scopes, then global

Interview tip: Scope chain means inner functions can access variables from outer functions, but outer functions cannot access inner function variables.

Scope यह तय करता है कि variables कहाँ accessible हैं। JavaScript में global scope, function scope, और block scope (let/const के साथ) होता है।

let global = 'I am global';

function outer() {
    let outerVar = 'outer';
    
    function inner() {
        let innerVar = 'inner';
        console.log(innerVar);   // 'inner'
        console.log(outerVar);   // 'outer'
        console.log(global);     // 'I am global'
    }
    inner();
}
outer();

Scope Type	Description
Global scope	Variables everywhere accessible
Function scope	सिर्फ function के अंदर accessible
Block scope	सिर्फ block (if, for) के अंदर (let/const)
Scope chain	JavaScript local से फिर parent scopes से फिर global से खोजता है

इंटरव्यू टिप: Scope chain का मतलब inner functions outer function के variables access कर सकते हैं, पर उल्टा नहीं।

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