JavaScript
The programming language of the web.
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This course has 7 lessons. Start with the first one and use the next / previous links at the bottom of each lesson — the sidebar keeps the whole course in order.
Lessons
- JavaScript basicsVariables, the seven primitives, type coercion, and the == vs === decision that causes most beginner bugs.
- Functions and scopeParameters, defaults, arrow functions, closures and this — the ideas behind almost every JavaScript interview question.
- Arrays and iterationThe methods that replace most for-loops — map, filter, reduce, find — and when mutation versus copying matters.
- Objects and destructuringProperty shorthand, spread merging, optional chaining, and copying objects without the reference traps.
- Working with the DOMSelecting elements, reading and writing content safely, creating nodes, and why innerHTML deserves caution.
- EventsaddEventListener, bubbling and capturing, delegation for dynamic lists, and forms without page reloads.
- Async JavaScript and fetchPromises, async/await, real fetch usage with error handling, cancellation, and running tasks concurrently.
More in Front-end Development
Last refreshed 2026-09-17.