Top JavaScript Interview Questions Every Fresher Should Know
A curated list of JavaScript interview questions every fresher must know, with clear answers.
Top JavaScript Interview Questions Every Fresher Should Know
Freshers face predictable JavaScript interview questions, since JS fundamentals are the foundation of any frontend role. Here are the top ones with clear answers.
What is a closure?
A closure is a function that remembers the variables from where it was created, even after that outer function has returned. Closures let inner functions access outer variables.
What is the difference between let, const, and var?
var is function-scoped and hoisted. let and const are block-scoped. const cannot be reassigned. Use let for variables that change, const for those that do not, and avoid var.
What is hoisting?
Hoisting moves declarations to the top of their scope. var declarations are hoisted and initialized as undefined. let and const are hoisted but not initialized, causing a temporal dead zone.
What is the event loop?
The event loop is how JavaScript handles async operations on a single thread. It processes the call stack, then the microtask queue, then the task queue, letting async callbacks run when the stack is clear.
What is the difference between == and ===?
== compares with type coercion, converting types before comparing. === compares without coercion, requiring same type and value. Always use === to avoid unexpected conversions.
What is a promise?
A promise is an object representing the eventual result of an async operation. It has states: pending, fulfilled, rejected. Use then, catch, and async/await to work with promises.
What is this in JavaScript?
this refers to the object the function is called on. Arrow functions do not have their own this; they inherit from the surrounding scope. this changes with how the function is called, which confuses many beginners.
The Takeaway
Know these fresher JavaScript questions cold: closures, let/const/var, hoisting, the event loop, === vs ==, promises, and this. These fundamentals are the foundation interviewers test for freshers, and everything else builds on them.
A closure is a function that remembers the variables from where it was created, even after that outer function has returned. Closures let inner functions access outer variables, which is foundational for callbacks and data privacy.
var is function-scoped and hoisted. let and const are block-scoped. const cannot be reassigned. Use let for variables that change, const for those that do not, and avoid var in modern code.
Hoisting moves declarations to the top of their scope. var declarations are hoisted and initialized as undefined. let and const are hoisted but not initialized, causing a temporal dead zone if accessed before declaration.
How JavaScript handles async on a single thread. It processes the call stack, then the microtask queue (promises), then the task queue (setTimeout, events), letting async callbacks run when the stack is clear.
== compares with type coercion, converting types before comparing, which can cause unexpected results. === compares without coercion, requiring same type and value. Always use === to avoid bugs from unexpected conversions.
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