Stage 1 · Lesson 3 of 9
Arrays, objects and destructuring
Screens are built from arrays of objects, so learn to work with them fluently. The array methods map, filter, find, some, reduce and sort cover most data preparation. map is how you turn data into list items.
pulls values out of an object or array, as in const { title, author } = post or const [first, ...rest] = items. You will see it in every component signature. The spread operator copies, as in { ...post, likes: 3 }. Use Map and Set when keys are not strings or you need a fast "is it in there?" check.
Common trapsort and reverse: they change the original array, which can silently corrupt state you meant to leave alone.
A question to check yourself, an AI practice session and 1 cheat sheet entry come with the full roadmap. Unlock
Resources for this stage
Start with· follow one of these
- CoursePaidGrokking JavaScript Fundamentals
Design Gurus · Beginner · $50
Beginner JavaScript with an exercise after most lessons
- GuideFreeJavaScript.info
Ilya Kantor
Free and thorough: Part 1 is the language, skip the browser chapters in Part 2