Posts tagged javascript

What useEffect really does, when it runs, and how the dependency array and cleanup function work. Simple examples for fetching data, timers and page titles.

Learn the JavaScript array methods you will use daily: map, filter, find, some, every, reduce and sort, with runnable examples on one shopping cart.

Learn what Express middleware is, how next() moves a request through the pipeline, and how to write a logger, an API-key gate and an error handler.

Build your first REST API with Node.js and Express in about 50 lines: routes, JSON, POST, PUT and DELETE, tested with curl, plus where to go next.

Learn how REST APIs work by following one request from client to server and back: URLs, methods, headers, status codes, JSON, and what REST actually means.

Python or JavaScript as your first language? See the same program written both ways, where each trips beginners up, and why JavaScript takes you furthest.

useState or useReducer? See the same cart built both ways, the signs it's time to switch, and a simple rule of thumb for choosing in your React components.

A plain-English guide to JavaScript async/await: what it really does, how it relates to promises, and the mistakes that trip people up.

You copied an array, changed the copy, and the original changed too. Here is what a JavaScript variable actually holds and how to copy safely.

You can read JavaScript but keep forgetting how to write it. The difference between an expression and a statement explains most of the syntax.

Learn JavaScript closures with tested examples: counters, the var vs let loop question, private state, debounce, and the stale closure bug in React hooks.