*A–Z of JavaScript programming concepts* 🚀 *A – Async/Await* Handles asynchronous operations in a cleaner way compared to promises. ```js async function fetchData() { let response = await fetch('https://api.example.com/data'); let data = await response.json(); console.log(data); } ``` *B – Browser Events* Handles user interactions using event listeners like `click`, `keydown`, etc. ```js document.addEventListener('click', () => console.log('Clicked!')); ``` *C – Closures* Functions that retain access to their parent scope even after execution. ```js function outer() { let count = 0; return function inner() { count++; return count; }; } ``` *D – DOM (Document Object Model)* JavaScript interacts with HTML elements through the DOM. ```js document.getElementById('myDiv').innerText = "Hello!"; ``` *E – ES6 (ECMAScript 2015+)* Major update introducing `let`, `const`, arrow functions, template literals, etc. *F – Fetch API* Modern way to handle HTTP requests instead of `XMLHttpRequest`. ```js fetch('https://api.example.com/data') .then(response => response.json()) .then(data => console.log(data)); ``` *G – Generators* Functions that yield multiple values lazily. ```js function* generateNumbers() { yield 1; yield 2; yield 3; } ``` *H – Hoisting* JavaScript moves declarations to the top during execution. ```js console.log(a); // Undefined (not an error) var a = 10; ``` *I – Immediately Invoked Function Expressions (IIFE)* Functions that execute immediately after definition. ```js (function () { console.log('IIFE runs instantly!');})(); ``` *J – JSON (JavaScript Object Notation)* Lightweight data format widely used in APIs. ```js const jsonData = '{"name": "Alice", "age": 30}'; const obj = JSON.parse(jsonData); ``` *K – Key-Value Pairs (Objects)* Objects store data in key-value format. ```js const user = { name: "John", age: 25}; ``` *L – Lexical Scope* Variables are accessible within the scope they’re declared. *M – Map Object* Stores key-value pairs but allows object keys as well. ```js const map = new Map(); map.set('name', 'Alice'); ``` *N – Null vs Undefined* `null` is an intentional absence of value, while `undefined` means uninitialized. *O – Object-Oriented Programming (OOP)* Supports class-based or prototype-based inheritance. ```js class Car { constructor(model) { this.model = model; } } ``` *P – Promises* Handles asynchronous operations cleanly. ```js let promise = new Promise((resolve, reject) => { resolve("Success!");}); ``` *Q – Query Selector* Easily selects elements in the DOM. ```js document.querySelector('.myClass'); ``` *R – Reduce Method* Processes array values into a single result. ```js const nums = [1, 2, 3]; const sum = nums.reduce((acc, val) => acc + val, 0); ``` *S – Spread & Rest Operators* Expands or collects values in arrays or objects. ```js const arr1 = [1, 2, 3]; const arr2 = [...arr1, 4, 5]; // Spread function sum(...numbers) { return numbers.reduce((a, b) => a + b);} // Rest ``` *T – Ternary Operator* Shortens `if-else` statements. ```js const result = age> 18? "Adult": "Minor"; ``` *U – Use Strict Mode* Helps write cleaner JavaScript. ```js 'use strict'; ``` *V – Variables (`var`, `let`, `const`)* Modern JavaScript favors `let` and `const` over `var`. *W – Web APIs* JavaScript can access browser features like *Local Storage*, *Canvas*, and *Geolocation*. *X – XMLHTTPRequest* Older method for making HTTP requests before `fetch()`. *Y – Yield (Generators)* Pauses function execution until `next()` is called. *Z – Zero-Based Indexing* Arrays start indexing from zero. 💬 *React ❤️ if this was helpful!*🚀