Deep understanding of the language — not just syntax, but the runtime: closures, prototypes, async, and the event loop.
JavaScript powers interactivity on every web page.
Must-know fundamentals:
- Variables (var/let/const), hoisting, TDZ
- Functions, closures, lexical scope
- Prototype chain & class syntax
- Asynchronous JS: callbacks → Promises → async/await
- Event loop, call stack, microtask queue
- DOM manipulation & events
- Fetch API & XMLHttpRequest
- ES6+ features: destructuring, spread/rest, optional chaining, nullish coalescing, modules
- Error handling: try/catch, custom Error classes
Debugging:
- Chrome DevTools (breakpoints, network tab, performance profiler)
- console methods beyond console.log
Must-know fundamentals:
- Variables (var/let/const), hoisting, TDZ
- Functions, closures, lexical scope
- Prototype chain & class syntax
- Asynchronous JS: callbacks → Promises → async/await
- Event loop, call stack, microtask queue
- DOM manipulation & events
- Fetch API & XMLHttpRequest
- ES6+ features: destructuring, spread/rest, optional chaining, nullish coalescing, modules
- Error handling: try/catch, custom Error classes
Debugging:
- Chrome DevTools (breakpoints, network tab, performance profiler)
- console methods beyond console.log