javascript_70_questions
javascript面试70问
The 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?