JSIQ
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Questions

  • What's the difference between undefined and null?
  • What does the && operator do?
  • What does the || operator do?
  • Is using the + or unary plus operator the fastest way in converting a string to a number?
  • What is the DOM?
  • What is Event Propagation?
  • What's Event Bubbling?
  • What's Event Capturing?
  • What's the difference between event.preventDefault() and event.stopPropagation() methods?
  • How to know if the event.preventDefault() method was used in an element?
  • Why does this code obj.someprop.x throw an error?
  • What is event.target ?
  • What is event.currentTarget?
  • What's the difference between == and === ?
  • Why does it return false when comparing two similar objects in JavaScript?
  • What does the !! operator do?
  • How to evaluate multiple expressions in one line?
  • What is Hoisting?
  • What is Scope?
  • What are Closures?
  • What are the falsy values in JavaScript?
  • How to check if a value is falsy?
  • What does "use strict" do?
  • What's the value of this in JavaScript?
  • What is the prototype of an object?
  • What is an IIFE, what is the use of it?
  • What is the use Function.prototype.apply method?
  • What is the use Function.prototype.call method?
  • What's the difference between Function.prototype.apply and Function.prototype.call?
  • What is the usage of Function.prototype.bind?
  • What is Functional Programming and what are the features of JavaScript that makes it a candidate as a functional language?
  • What are Higher Order Functions?
  • Why are functions called First-class Objects?
  • Implement the Array.prototype.map method by hand.
  • Implement the Array.prototype.filter method by hand.
  • Implement the Array.prototype.reduce method by hand.
  • What is the arguments object?
  • How to create an object without a prototype?
  • Why does b in this code become a global variable when you call this function?
  • What is ECMAScript?
  • What are the new features in ES6 or ECMAScript 2015?
  • What's the difference between var, let and const keywords?
  • What are Arrow functions?
  • What are Classes?
  • What are Template Literals?
  • What is Object Destructuring?
  • What are ES6 Modules?
  • What is the Set object and how does it work?
  • What is a Callback function?
  • What are Promises?
  • What is async/await and How does it work?
  • What's the difference between Spread operator and Rest operator?
  • What are Default Parameters?
  • What are Wrapper Objects?
  • What is the difference between Implicit and Explicit Coercion?
  • What is NaN? and How to check if a value is NaN?
  • How to check if a value is an Array?
  • How to check if a number is even without using the % or modulo operator?
  • How to check if a certain property exists in an object?
  • What is AJAX?
  • What are the ways of making objects in JavaScript?
  • What's the difference between Object.seal and Object.freeze methods?
  • What's the difference between the in operator and the hasOwnProperty method in objects?
  • What are the ways to deal with Asynchronous Code in JavasScript?
  • What's the difference between a function expression and function declaration?
  • How many ways can a function be invoked?
  • What is memoization and what's the use it?
  • Implement a memoization helper function.
  • Why does typeof null return object? How to check if a value is null?
  • What does the new keyword do?
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