🚀 “What Are the Different Types of Functions in JavaScript?”
It sounds like a basic question.
But in senior interviews, it’s rarely about listing syntax.
It’s about whether you understand how functions define JavaScript’s architecture.
Here’s how I would break it down in a real interview 👇
🔹 Regular (Named) Functions
"function greet() {}"
They’re hoisted, reusable, and show up clearly in stack traces. Ideal for utility logic and shared modules.
🔹 Function Expressions
"const greet = function() {}"
Not hoisted like declarations. Often used in closures and callbacks where execution order matters.
🔹 Arrow Functions
"() => {}"
Not just shorter syntax. They don’t bind their own "this".
That makes them powerful in React components, event handlers, and async flows where lexical "this" avoids common bugs.
🔹 Higher-Order Functions
Functions that accept or return other functions.
Examples: "map", "filter", "reduce", middleware, custom hooks.
This is where JavaScript leans into functional programming.
🔹 Callback Functions
Functions passed to other functions for later execution.
They power async patterns — from traditional callbacks to Promises and async/await.
🔹 Pure Functions
Same input → same output. No side effects.
Crucial in reducers, memoization, and predictable state management.
🔹 IIFE (Immediately Invoked Function Expression)
"(function(){})()"
Historically used for scope isolation before ES6 modules existed.
🔹 Curried Functions
Functions returning functions:
"add(2)(3)"
Used for partial application and reusable, composable logic.
🔹 Constructor Functions
Used with "new" to create instances before ES6 classes.
They introduced prototype-based inheritance.
🔹 Generator Functions
"function*"
Pause and resume execution with "yield". Useful for custom iterators and controlled async flows.
💬 Interview insight
Don’t stop at naming types.
Connect them to real use cases: state management, async control, performance, architecture decisions.
That’s what turns a simple question into a senior-level discussion.
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Yeah, no doubt - this is the basics, must have to know