JavaScript
The programming language of the web — runs in every browser and powers both frontend interfaces and Node.js backend services.
JavaScript is the foundational language for web development. While TypeScript has overtaken it as the professional standard, JavaScript knowledge is prerequisite to everything built on top of it — React, Node.js, Next.js, and every major web framework. It is the most widely deployed programming language in existence.
Typical time to job-readiness: ~4 months.
Learning JavaScript
Beginner
Master the fundamentals — variables, functions, arrays, objects, DOM manipulation, and async (promises, async/await). Build projects that consume real APIs.
Intermediate
Understand closures, the event loop, ES modules, and prototype chains. Learn to debug effectively and handle error states gracefully.
Advanced
Deep spec knowledge (generators, Proxy, WeakMap), performance profiling, and memory management. Senior roles expect you to explain unexpected behavior, not just fix it.
Key concepts
- The event loop, call stack, and task queue — why JS is single-threaded
- Closures and lexical scope — how functions remember their environment
- Prototypal inheritance and the prototype chain
- Promises, async/await, and handling async errors correctly
- ES6+ features: destructuring, spread/rest, modules, optional chaining
- How 'this' binding works across function types
Common interview topics
- Explain how the JavaScript event loop works
- What is a closure and give a practical example of its use
- Explain the difference between == and === and when each applies
- How does 'this' work in arrow functions vs regular functions
- What is the difference between var, let, and const
- How does promise chaining work and how do you handle errors