Variable Scope — JS Technical Interview Questions & Answers

Global, function and block scope.

Variable Scope

  • Variable Scope (js) is a JS topic. In plain words you use it for let total = 0 in a cart script. Don’t start with a slogan — start with that picture.
  • Smallest example: let for change, const for fixed. Type it, run it, and say what you see. If you can do that from memory, you know Variable Scope (js).
  • From the example next to this theory: Global, function and block scope.
  • Trap: var leak / const reassign. Fix that before you talk about advanced JS.
  • Viva: what is Variable Scope (js)? Then show let for change, const for fixed. Then name the trap.

Technical Interview Tip: What is Variable Scope (js)? Show this: let for change, const for fixed. Trap: var leak / const reassign.

Code Examples for Variable Scope

Variable Scope — working example

function demo() {
  if (true) {
    var a = 1;
    let b = 2;
    const c = 3;
    console.log(b, c);
  }
  console.log(a); // 1 — var is function-scoped
  // console.log(b); // ReferenceError — let is block-scoped
}
demo();
console.log(typeof undeclaredVar); // undefined (never declared with let/const)

Variable Scope — var is function-scoped and hoisted; let/const are block-scoped. Prefer const, then let.

How to Explain Variable Scope to an Interviewer

What is Variable Scope (js)?

Used for let total = 0 a cart script Not just the heading

Give one small example of Variable Scope (js).

let for change, const for fixed Global, function and block scope

What mistake do beginners make with Variable Scope (js)?

var leak / const reassign Show the fix

Where do you use Variable Scope (js)?

a cart script let total = 0