The latest front end of the interview questions summary (including analysis)

“This is the 9th day of my participation in the Gwen Challenge in November. Check out the details: The Last Gwen Challenge in 2021.”

preface

Last month captured the cattle 21 years of the latest pen test questions and face test questions, pen test questions issued last month, was not prepared, did not prepare the answer. Face by part of the topic I absorb the last lesson, each topic I prepare the answer, some of the answer is my understanding, some of the topic my level may be temporarily limited, the answer is selected to dig gold high praise high volume blog. I hope it helps.

In the interview section, the preliminary decision is divided into two parts, one for all short answer questions and handwritten questions, and the other for procedural questions. This chapter is a short answer and handwritten section.

We are trying to figure out how to post it in the programming section, and you can also post your thoughts in the comments section

I have made statistics about the front-end questions of about 15 big companies in Niuke, and the frequency of investigation is roughly divided as follows:

⭐⭐⭐⭐ service: 10+ in 15 company interviews
⭐⭐⭐⭐ : 5-10 in 15 formula interviews
⭐⭐⭐ : 3-5 in interviews with 15 companies
No star: 1-2 appears

Here are the questions section and the question analysis section portal:

Cow guest latest front-end JS written test 100 questions
Grab the latest front end test five hundred data analysis JS interview hot spots

JavaScript Basics

Typeof problem summary

(⭐⭐⭐⭐⭐)

Answer & Analysis

Does Typeof distinguish between raw values correctly

What are the return values of typeof

What does typeof Function display

Why does Typeof display null errorsAnswer & Analysis

Typeof (‘ ABC ‘) and typeof ‘ABC’ are both strings, so is typeof an operator or a function?Answer & Analysis

JavaScript data type

(⭐⭐⭐⭐⭐)

Answer & Analysis

== implicit conversion rule

Undefined and null are themselves equal and mutually equal

(⭐⭐⭐⭐⭐)

== implicit conversion rule

Instanceof principle

(⭐⭐⭐)

Answer & Analysis

[“1″,”2″,”3”]. What is the result of map(parseInt) and explain why

How to return the above formula [1,2,3] using the simplest solution you can think of (require using [].map()))

(⭐⭐⭐)

Answer & Analysis

A method for determining data types

Answer & Analysis

Differences between Typeof and Instanceof

Answer & Analysis

How to determine the array type

Answer & Analysis

Number Indicates the maximum range of integers that can be represented

Answer & Analysis

2. What will be printed by toFixed()

Answer & Analysis

A method of querying whether an object has a property

Answer & Analysis

What’s the difference between splice and slice

Answer & Analysis

== and ===

Answer & Analysis

The difference between a constructor and a normal function

Answer & Analysis

Class array is different from array, why set class array

Answer & Analysis

Null and undefined

Answer & Analysis

A.B.C.D or a[‘b’][‘c’][‘ D ‘], which is better?

Answer & Analysis

ForEach or for loop, which performs better

Answer & Analysis

JavaScript In Depth

This points to the

(⭐⭐⭐⭐⭐)

Answer & Analysis

Prototype and prototype chain

(⭐⭐⭐⭐⭐)

Answer & Analysis

Can you talk a little bit about the event loop?

(⭐⭐⭐⭐⭐)

Answer & Analysis

Scope and scope chain

(⭐⭐⭐⭐⭐)

Answer & Analysis

Talk about your understanding of closures

(⭐⭐⭐⭐⭐)

Answer & Analysis

precompiled

(⭐⭐⭐⭐⭐)

Answer & Analysis

What does the new operator do

(⭐⭐⭐⭐⭐)

Answer & Analysis

Garbage collection mechanism

(⭐⭐⭐⭐)

“Hardcore JS” Do you really understand garbage collection

The various ways and advantages of inheritance

(⭐⭐⭐⭐)

Answer & Analysis

JS prototype chain inheritance and Class inheritance

(⭐⭐⭐⭐)

Answer & Analysis

Call, apply, bind

(⭐⭐⭐⭐)

Answer & Analysis

Cookie, localStorage sessionStorage difference

(⭐⭐⭐⭐)

Answer & Analysis

Array higher-order methods

(⭐⭐⭐⭐)

Answer & Analysis

The difference between anti-shake and throttling

(⭐⭐⭐⭐)

Answer & Analysis

What is the difference between the script tag defer and the async attribute

(⭐⭐⭐)

Answer & Analysis

The difference between synchronous and asynchronous tasks

(⭐⭐⭐)

Answer & Analysis

Constructor, instance object and prototype object relationship

(⭐⭐⭐)

Answer & Analysis

If I call a function with new and the function has a return, what does it return

(⭐⭐⭐)

Answer & Analysis

SetTimeout, Promise, Async/Await

Answer & Analysis

17. What does _proto_ of Object refer to

Answer & Analysis

18. What does the _proto_ of Function point to

Answer & Analysis

19. What tasks are Promise and setTimeout respectively

Answer & Analysis

20. Why is the js file placed at the bottom of the file

Answer & Analysis

ES6

What is promise? Make a simple promise

(⭐⭐⭐⭐⭐)

Promise won’t…? Look here!! The most accessible Promise ever!!

Promise.all(),.race(),.allSettled() contrast

(⭐⭐⭐⭐⭐)

The three brothers in Promise.all(),.race(),.allsettled ()

The difference between Promise, Generator and Async

(⭐⭐⭐⭐⭐)

Answer & Analysis

Async and await principle

(⭐⭐⭐⭐⭐)

Answer & Analysis

Let const var

(⭐⭐⭐⭐⭐)

Answer & Analysis

Arrow functions are different from normal functions

(⭐⭐⭐⭐⭐)

Answer & Analysis

DefienProperty is different from proxy

(⭐⭐⭐⭐)

Answer & Analysis

Difference between Map and weakMap

(⭐⭐⭐⭐)

Answer & Analysis

Set is different from weakSet

(⭐⭐⭐⭐)

Answer & Analysis

The difference between map and Object

(⭐⭐⭐⭐)

Answer & Analysis

The map to set

(⭐⭐⭐⭐)

Understand Map and Set in ES6 thoroughly

How to handle exceptions gracefully while using async & await

(⭐⭐⭐⭐)

How to handle exceptions gracefully while using async & await

The proxy pros and cons

(⭐⭐⭐)

Interviewer: How better is implementing a two-way binding Proxy than defineProperty?

Object.defineProperty

(⭐⭐⭐)

Answer & Analysis

Introduce symbol

(⭐⭐⭐)

Answer & Analysis

Can proxy listen for changes to nested objects

Answer & Analysis

Do you know ES6 bigInt

Answer & Analysis

Map and Object key traversal sequence

Answer & Analysis

Talk about Promise value penetration and exception penetration

Answer & Analysis

Object.assign Is a shallow copy or a deep copy? What are the ways to implement deep copy? (2020.01.07). The md

Answer & Analysis

Underlying Principles of Generator

Answer & Analysis

BOM DOM

The DOM event flow

Event bubbling, event capture

What is event delegation?

What are the apis that get the element’s position on the page

SetTimeout is different from setInterval, which is more accurate

▌ The timer is not on time. ▌ setTimeout and setInterval

In timer = setInterval(() => {}, delay), what does the timer print out

requestAnimationFrame

traverse

A method to traverse an object

For in 和 Object. Keys

The difference between for in and for of

Can for of iterate over objects

Hand code

promise

Realize the promise

(⭐⭐⭐⭐⭐)

Reference code

Realize the promise. All

(⭐⭐⭐⭐⭐)

Reference code

Realize the promise. Finally

(⭐⭐⭐⭐⭐)

Reference code

Realize the promise. AllSettled

(⭐⭐⭐⭐)

Reference code

Realize the promise. Race

(⭐⭐⭐)

Reference code

How do you execute multiple promises sequentially

Reference code

promise.any

Reference code

resolvev reject

Reference code

Array article

Array to heavy

(⭐⭐⭐⭐⭐)

Reference code

Array flattening

(⭐⭐⭐)

Reference code

forEach

(⭐⭐⭐)

Reference code

reduce

(⭐⭐⭐)

Reference code

map

Reference code

filter

Reference code

every

Reference code

some

Reference code

find/findIndex

Reference code

indexOf

Reference code

To achieve the sort

Reference code

If the throttle

Implement the anti-shock function debounce

(⭐⭐⭐⭐⭐)

Reference code

Implement throttle functions

(⭐⭐⭐⭐⭐)

Reference code

The Object article

Can you write a full deep copy

(⭐⭐⭐⭐⭐)

Reference code

Implement new

(⭐⭐⭐⭐)

Reference code

inheritance

(⭐⭐⭐⭐)

Prototype chain inheritance

Borrowing constructors (classical inheritance)

Combination of inheritance

Primary inheritance

Parasitic inheritance

Parasitic combinatorial inheritance

Class implementation inheritance (sidebar)

class Animal {
    constructor(name) {
        this.name = name
    } 
    getName() {
        return this.name
    }
}
class Dog extends Animal {
    constructor(name, age) {
        super(name)
        this.age = age
    }
}
Copy the code

Reference code

To realize the object. The create

Reference code

The Function post

call

(⭐⭐⭐⭐)

Reference code

bind

(⭐⭐⭐⭐)

Reference code

apply

(⭐⭐⭐⭐)

Reference code

Implement creefaction

(⭐⭐⭐)

Reference code

Implement chain calls

Reference code

Partial function

Reference code

Ajax and json

(⭐⭐⭐)

Implementing ajax

Reference code

To realize the json

Reference code

ES6 article

To achieve the set

Reference code

To realize the map

Reference code

Implement es6 class

Reference code

Use proxy to achieve arR negative index access

Reference code

other

instanceof

(⭐⭐⭐⭐)

Reference code

Implement thousandth delimiters

(⭐⭐⭐)

Reference code

Convert the key of a JSON object from underscore (Pascal) to Camel

(⭐⭐⭐)

Reference code

Implement data type judge function

Reference code

Implement array to tree

Reference code

Implementing the sleep function

Reference code

Implement the publish and subscribe model

Reference code

The answer question is not found

Set de-duplication principle

Use promise to implement request timeout rerequests

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