Gyaan

JavaScript

Core JS concepts: closures, event loop, prototypes, and more.

43 notes View all on one page

Fundamentals

1

let, const, and var

Understanding the differences between var, let, and const declarations.

beginner variables ES6 scope
2

Data Types & Type Coercion

Primitive vs reference types, typeof quirks, loose vs strict equality, truthy/falsy values, and coercion gotchas.

beginner types coercion equality
3

Hoisting

How JavaScript moves declarations to the top of their scope before execution — var, let/const, functions, and the Temporal Dead Zone.

beginner hoisting scope TDZ
4

use strict

Strict mode makes it easier to write secure JavaScript by turning bad syntax into real errors.

beginner strict-mode best-practices
5

Destructuring

Extracting values from objects and arrays into variables using concise syntax.

beginner ES6 destructuring objects
6

Spread & Rest Operators

The ... syntax serves two purposes — spread expands elements, rest collects them.

beginner ES6 spread rest
7

Template Literals

String interpolation, multi-line strings, and tagged templates using backtick syntax.

beginner ES6 strings template-literals

Functions

8

Arrow Functions

ES6 arrow functions allow shorter function syntax.

beginner ES6 functions
9

Higher-Order Functions

Functions that take other functions as arguments or return functions — the foundation of functional JavaScript.

intermediate functions functional-programming array-methods
10

Closures

A closure gives you access to an outer function's scope from an inner function.

intermediate scope functions lexical-environment
11

Currying

Transformation of a function with multiple arguments into several functions of a single argument.

intermediate functional-programming functions
12

Memoization

Optimization technique that stores results of expensive function calls and returns cached results.

intermediate performance optimization caching
13

Call, Apply and Bind

Methods to explicitly set the 'this' context when calling functions.

intermediate this functions context
14

IIFE (Immediately Invoked Function Expression)

Functions that run as soon as they are defined — used for scoping and avoiding global pollution.

intermediate functions scope IIFE

Async JavaScript

19

Callbacks

Understanding callbacks — functions passed as arguments — and the problem of callback hell.

beginner callbacks async callback-hell
20

Promises

Understanding Promises — the modern way to handle asynchronous operations with then, catch, and chaining.

intermediate promises async then
21

Async/Await

Writing asynchronous code that looks synchronous using async functions and the await keyword.

intermediate async await promises
22

Promise Methods

Understanding Promise.all, Promise.allSettled, Promise.race, and Promise.any — when to use which.

intermediate promises async Promise.all
23

Error Handling

Handling errors gracefully with try/catch/finally, custom errors, and async error patterns.

intermediate errors try-catch async
24

Event Loop

How JavaScript handles asynchronous operations through the call stack, callback queue, and microtask queue.

advanced async event-loop runtime
25

Debouncing and Throttling

Techniques to control how often a function is executed in response to rapid events.

intermediate performance events optimization

DOM & Events

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Events

JavaScript's interaction with HTML through events that occur when the user or browser manipulates a page.

beginner DOM events browser
32

Event Bindings

Binding events to HTML elements using addEventListener or onclick attribute.

beginner DOM events
33

Event Propagation, Bubbling and Capturing

How events travel through the DOM — capturing phase (parent to child), target phase, and bubbling phase (child to parent).

intermediate DOM events propagation
34

Event Delegation

A pattern to handle events efficiently by adding a single listener to a parent element.

intermediate DOM events patterns
35

DOM Manipulation

Selecting, creating, modifying, inserting, and removing elements from the DOM.

beginner DOM elements browser
36

Web Storage & Cookies

Understanding localStorage, sessionStorage, and cookies — when to use which and how they differ.

beginner storage localStorage sessionStorage