JavaScript Fundamentals Interview Questions You Can't Skip

JavaScript Fundamentals Interview Questions You Can't Skip

Some JavaScript fundamentals are guaranteed to come up in interviews. Here are the ones you cannot skip.

let, const, var

Know scoping, hoisting, and the temporal dead zone. Be able to explain when each is appropriate and why var is avoided in modern code.

Arrow Functions vs Regular Functions

Know that arrow functions do not have their own this or arguments, and cannot be used as constructors. They are shorter and inherit this, which is why they are common in callbacks.

Closures

Know what a closure is, why it exists, and real use cases (data privacy, callbacks, once, memoize). Closures are tested in almost every JS interview.

The Event Loop and Async

Know the call stack, microtasks, macrotasks, and how promises and setTimeout fit in. Async behavior is a huge topic and is tested heavily.

Promises and async/await

Know promise states, chaining, error handling, and how async/await maps to promises. Be able to write async code that handles errors correctly.

Prototypes and this

Know the prototype chain, how this is determined by call site, and how arrow functions differ. These are foundational and frequently asked.

Equality and Coercion

Know === vs ==, type coercion rules, and truthy/falsy values. These come up in coding problems and direct questions.

The Takeaway

Do not skip these JS fundamentals: let/const/var, arrow vs regular functions, closures, the event loop, promises and async/await, prototypes and this, and equality and coercion. They come up in almost every JS interview.