Stage 1 · Lesson 4 of 8
JavaScript values, functions and scope
In this roadmap JavaScript runs in the browser and, for most stacks, on the server too. Gaps here show up everywhere. Learn let and const, and skip var.
Learn the difference between primitives (numbers, strings, true and false) and objects. Objects are shared by reference: if a function changes one, the caller sees the change. Use === rather than ==, and learn which values count as .
Get fluent with , , spread and the array methods map, filter, find and reduce, because React code is full of them. Understand scope and : a function remembers the variables around the place where it was created.
Common trapchanging an array or object you meant to copy, which becomes a real bug once is involved.
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
Guided course on the language core if you want structure and quizzes
- CourseFreeThe Odin Project
The Odin Project · Beginner
Free Foundations course: HTML, CSS and JavaScript built in your own editor
Practise
Keep handy
Also worth your time
The request path from browser to server that the rest of this roadmap builds on