javascript interview questions

• transpilation and compilation
• unknown in ts
• generics
• How to check if an object is an array or not? Provide some code
• Lexical scope
• Difference between const, let and var.
• what isNaN function does?
• Scope in JavaScript function
• Hoisting in js
• Ecma6 feat
• What is context in JS?
• Difference between map, reduce and filter
• Difference between class and function
• Normal Function vs Arrow function
• Difference between async and defer
• Difference between == and ===
• Difference between setTimeout and setInterval
• What are the different DOM API’s
• DOM vs Virtual DOM
• How Event loop works
• What is event delegation
• Difference between call, bind and apply
• Explain Promise
• Throttling vs Debouncing
• What is Closure and why should we use closure
• What are the different internal storage and its differences
• What is variable hoisting
• Difference between document.ready(){} and window.onload(){}
• What is async, preload, prefetch in script
• Callback vs Promise
• Explain Currying
• Questions related to flatten array
• Call by value vs Call by reference
• Prototypal inheritance
• How do you optimize page performance
• Write polyfill for Filter, Reduce, Promise
• DOM Traversal, Manipulation & Creating Elements
• core principles: (JS fundamentals)
• Functions are first-class citizens in JavaScript
• Objects (e.g. Object.keys(myObj).map(key => myMap[key]))
• Arrays (e.g. [1, 2].reduce((sum, summand) => sum + summand, 0))
• Prototypical Inheritance -> ES6 Class
• Callbacks and Promises
• Event Loop
• Regular Expressions
• Error handling (promise.then(...).catch(...), try { } catch(e) { })
• JavaScript ES6 and beyond
• Hoisting, Memoization
• Declarative vs imperative programming
• Functional vs object-oriented programming
• Inheritance vs composition
• Inheritance types- Single, Multi-level, Multiple
• composition types- object, function, class
• Functions - Factory , Generator, pure and Non-pure
• objects
• hashmap
• shallow and deep copy
• polyfills
• recursive problems - flatten object
• event loop - how heap works -> event loop handles the recursion, not the call stack
• Call Stack, Memory Heap, Event Queue, and Event Loop
• main thread and secondary thread
• critical rendering path - browser app load
• caching - server
• cors and proxy
• temporal dead zone
• global, local, lexical
• hoisting
• v8 and libuv
• IIFEs
• this keyword
• ES6 features - WeakMap, set, WeakSet
• Babel
• solid principle
• Four principles of OOP-Encapsulation, Abstraction, Inheritance, Polymorphism
• Rest vs spread
• context
• Prototype
• defer and async
• Event Bubbling and Capturing
• Static method
• Method decorators