JavaScript Interview Questions for Freshers (20 Real Questions with Answers)

A closure is a function that remembers its outer variables even when executed outside its original scope.

'==' checks for value equality with type coercion. '===' checks for strict equality (value and type).

The Event Loop monitors the Call Stack and Callback Queue. If the Stack is empty, it pushes the first task from the Queue to the Stack.

'this' refers to the object it belongs to. In global scope, it's window. In a method, it's the owner object.

A Promise is an object representing the eventual completion or failure of an asynchronous operation.

Hoisting is JavaScript's behavior of moving declarations to the top of the scope before execution. Variables (var) and functions are hoisted.

var is function-scoped and hoisted. let and const are block-scoped. const cannot be reassigned.

Every object has a prototype. If a property isn't found on the object, JS looks up the prototype chain until it finds it or hits null.

Immediately Invoked Function Expression. It runs as soon as it is defined. Used to avoid polluting the global scope.

Currying is transforming a function with multiple arguments into a sequence of functions each taking a single argument.

undefined means a variable has been declared but not defined. null is an assignment value representing 'no value'.

Event bubbling is when an event triggers on the deepest element and then bubbles up to its parents.

Using JSON.parse(JSON.stringify(obj)) or libraries like Lodash. Recently, structuredClone() is also supported.

Debouncing enforces that a function is not called again until a certain amount of time has passed since its last call. Good for search inputs.

Throttling enforces a maximum number of times a function can be called over time. Good for resize/scroll events.

A concise syntax for writing function expressions. They do not have their own 'this' or 'arguments' binding.

map creates a NEW array with the results. forEach executes a function for each element but returns undefined.

A function that always produces the same output for the same input and has no side effects.

A syntax that allows you to unpack values from arrays, or properties from objects, into distinct variables.

The (...) operator expands an iterable (like an array) into individual elements. Useful for copying or merging.

Closures, the event loop, promises/async-await, hoisting, and '==' vs '===' — the first five questions in this bank — appear in nearly every screening round in India.

Yes — destructuring, arrow functions, spread/rest, modules and template literals are assumed knowledge in 2026, not bonus points.

JavaScript rounds test the language itself; React rounds test the framework built on it. Weak JavaScript answers undermine strong React answers — prepare this bank first.