javascript

## What I do - Write modern JavaScript (ES6+) - Handle async operations with promises and async/await - Use array methods (map, filter, reduce) - Work with objects and arrays - Handle DOM manipulation - Use modules and imports - Implement error handling ## When to use me When building web applications or server-side code with Node.js. ## Variables & Types ```javascript // Let and const const PI = 3.14159; let count = 0; // Template literals const greeting = `Hello, ${name}!`; // Destructuring const { name, age } = user; const [first, second] = array; // Spread operator const copy = { ...original, newProp: value }; const merged = [...arr1, ...arr2]; ``` ## Arrays ```javascript const numbers = [1, 2, 3, 4, 5]; // Map, Filter, Reduce const doubled = numbers.map(n => n * 2); const evens = numbers.filter(n => n % 2 === 0); const sum = numbers.reduce((acc, n) => acc + n, 0); // Find const found = numbers.find(n => n > 3); const index = numbers.findIndex(n => n === 3); // Other methods numbers.includes(3); numbers.flatMap(x => [x, x * 2]); ``` ## Objects ```javascript const user = { name: 'John', age: 30, greet() { return `Hi, I'm ${this.name}`; } }; // Shorthand const name = 'John'; const obj = { name }; // Optional chaining const city = user?.address?.city; // Nullish coalescing const value = data ?? 'default'; ``` ## Async ```javascript // Promises fetch('/api/data') .then(res => res.json()) .then(data => console.log(data)) .catch(err => console.error(err)); // Async/await async function fetchData() { try { const res = await fetch('/api/data'); const data = await res.json(); return data; } catch (err) { console.error(err); } } // Parallel const [users, posts] = await Promise.all([ fetch('/api/users').then(r => r.json()), fetch('/api/posts').then(r => r.json()) ]); ``` ## Modules ```javascript // export.js export const API_URL = 'https://api.example.com'; export function fetchData() { } export default class MyClass { } // import.js import MyClass, { fetchData, API_URL } from './export.js'; ```