Stage 2 · Lesson 3 of 10
Arrays, objects, destructuring and array methods
Most frontend code takes data from an and turns it into something on screen, and that is array and object work. Learn the main . map transforms each item, filter keeps some, find gets one, some and every test them, and reduce builds a single result such as a total.
None of them change the original array, and map and filter give you a new one. pulls values out of an object: const { name, price } = product. Spread copies and merges: { ...user, name: "Ana" }.
Objects and arrays are . So two variables can point at the same array, and a change made through one shows up in the other. Frameworks rely on you making new copies instead of changing (mutating) the original, so the habit matters now.
Common trapusing sort, which changes the array in place, on data you meant to keep.
A question to check yourself, an AI practice session and 2 cheat sheet entries come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking JavaScript Fundamentals
Design Gurus · Beginner · $50
Guided beginner course on the language core, with quizzes after every chapter
- GuideFreeJavaScript.info
Ilya Kantor
Free and thorough: Part 1 for the language, Part 2 for the DOM and events, Part 3 for fetch
Practise
Keep handy
Also worth your time
- You Don't Know JS YetGo deeper
For when scope, this, coercion or async behaviour still feel like magic