JavaScript

JavaScript fundamentals, async behavior, browser/runtime concepts, and coding-round exercises.

Study order: Execution → Scope → Closures → this → Prototypes → Arrays and objects → Async → Exercises

• What is JavaScript? — What JavaScript is, why it exists, and where it runs.
• Execution Context and Call Stack — How JavaScript runs code step by step.
• Scope, Hoisting, var, let and const — How variable visibility and declaration behavior work.
• Closures — How functions remember variables from their outer scope.
• this Keyword — How this is decided in different call sites.
• Prototypes and Prototype Chain — How JavaScript objects inherit behavior.
• Arrays, Objects and Common Methods — Working with data using map, filter, reduce, spread, rest, and destructuring.
• Event Loop — Why asynchronous callbacks run after the current call stack.
• Promises and async await — How JavaScript represents and handles future async results.
• Error Handling — try/catch, throwing errors, and handling async failures.
• JavaScript Modules — CommonJS vs ES Modules and how imports/exports organize code.
• Debounce and Throttle — Control how often a function runs during frequent events.
• Classes in JavaScript — Class syntax over prototype-based behavior.
• Shallow Copy vs Deep Copy — How object copying works and where reference bugs come from.
• Memory Leaks in JavaScript — Common ways references stay alive longer than expected.
• Currying and Memoization — Function patterns often asked in interviews and coding rounds.
• Polyfills: map, filter and reduce — Implement common array methods from scratch.
• Implement Debounce and Throttle — Write reusable debounce and throttle helpers.
• Flatten Array and Deep Clone — Handle nested arrays and object copying safely.
• Promise Utilities — Implement Promise.all, sequential execution, retry, and timeout helpers.
• Event Emitter and LRU Cache — Build two common machine-coding round utilities.