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?

How to check if a value is falsy?

Use the Boolean function or the Double NOT operator !!

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