2021 scenery written examination summary

Two 、 Guangzhou Zhijing written examination

The novice here doesn't remember the order of the questions , So I wrote the title directly , Don't write the serial number ！

heavy load

Here, the question of rookie is yes , Just recorded the inspection points , I don't know what the title is ！ Directly above ：

Array native methods

The novice can also , So I didn't write a specific topic , Only the knowledge points of investigation are written , Generally remember to choose resort,js There is no resort Of , If you want to reverse sort , It can be passed in directly Comparison function by sort Provide sorting method ！

From small to large

arr.sort(function (x, y) {
    
    if (x < y) {
    
        return -1;
    }
    if (x > y) {
    
        return 1;
    }
    return 0;
});

From big to small

arr.sort(function (x, y) {
    
    if (x < y) {
    
        return 1;
    }
    if (x > y) {
    
        return -1;
    }
    return 0;
});

More array methods , see ：js Array （ summary ）

Methods that call functions

See the article ：http://c.biancheng.net/view/5700.html

JavaScript Provides 4 Function calls ：

1. General form of function call
2. Method call as object
3. Use call and apply Dynamic invocation
4. Use new Indirect invocation – Instantiation

Design patterns

The title is ： We need to monitor an event state , Let it actively notify when the state changes , What kind of design pattern is needed ?


Novice tutorial ： Design patterns

Function of interface

Link to this question on Niuke website ：https://www.nowcoder.com/questionTerminal/5ccf725b8e694f1f8e562b928470707f

Why are the others wrong , Niuke didn't answer online ！ The rookie asked , Waiting for answers ！

Wrote this , The rookie suddenly lost interest and went on writing , Because I feel that if I haven't learned design patterns or studied interfaces carefully , It doesn't make sense at all ！

The rookie is just a weak chicken front , I really haven't learned these , It seems that it will take time to learn again , Even if the rookie writes now , It's just a short-term memory , At most, you won't be wrong again when you encounter the original question , But really go deep or change the option , I think I can't do it basically ！

Here's a rookie to understand , Know what these are , There must be something to learn later , This knowledge is not to remember what is a pass ！

Type comparison conversion Judge

Here rookies have to roast , True type questions are too common , Readers are advised to make clear , And must always review , Don't review, don't remember , This is really a memory test , No thought at all , The premise for you to think about this problem is that you have to remember ！

Just like a rookie who wrote a blog about type conversion last month , But this month , I really don't remember what type is changed into what type is , Just remember the general method , But don't make mistakes easily ！

Here are three links ：

1. 2021 Yahong pen test questions 2
2. see Javascript Detailed explanation of the actual battle Harvest one
3. js Get the data type in

I often take exams here ：

undefined == null; //true
undefined === null; //false
NaN == NaN; //false
NaN != NaN  //true


typeof null;  // Object
null instanceof object // false


//  Comparison process 
[] == ![]
//  Put the right side  ![]  convert 
[] == false
//  Implicitly convert Boolean values to numbers 
[] == 0
//  Convert the left  [], call  []  Example of  valueOf  Method 
[] == 0
// valueOf  Method does not return a basic type value , Call again  toString  Method 
'' == 0
//  Implicitly convert a string to a number 
0 == 0
//  Return results 
true


//  Comparison process 
{
    } == !{
    }
//  Put the right side  !{}  convert  
{
    } == false
//  Implicitly convert Boolean values to numbers 
{
    } == 0
//  Convert the left  {}, call  {}  Example of  valueOf  Method 
{
    } == 0
// valueOf  Method does not return a basic type value , Call again  toString  Method 
'[object Object]' == 0
//  Implicitly convert a string to a number 
1 == 0
//  Return results 
false


1 + '1' == '1' + '1' == '11'
true + true == 1 + 1 == 2
4 + [] == '4' + '' == '4'
4 + {
    } == '4' + '[object Object]' == '4[object Object]'
4 + [1] == '4' + '1' == '41'
4 + [1, 2, 3, 4] == '4' + '1, 2, 3, 4' == '41,2,3,4'
'a' + + 'b' == 'a' + 'NaN' == 'aNaN'


'true' == true // false
'true' === true // false

Another important thing is String Boolean to Boolean ：

The rookie is confused now anyway , I can't remember at all ！ I hope readers can take a good look at these three articles ！

summary

There are actually a few questions here, but it feels like it's just a memory type （ The rookie was not sure , So I wrote it down ）, It is not difficult to ：

1. js A rounded function --> round()
2. XMLHttpRequest stay send() You need to call ？ --> open()
3. E-R When a graph is converted to a relational schema , Both entities and connections can be expressed as ？ --> Relationship

There are two more java The topic ：
One 、

char a;
int b;
float c;
double d;

a*b+d-c What is the type of ？–>double

Two 、

int a = 10;
double b = 3.14;

“A”+a+b What is the type of ？ --> String

Rookies only remember a little java, So at that time, I had to guess ： The first thing I think is Java It seems that it will be converted to high precision ; The second one is to press JavaScript The operation of ！

Anyway, anyway , That is, don't roll , If you rewind, you'll be an engineer of the whole stack , Split the front and back of the fart ！ Don't say the , Volume design mode went

By the way, I have good news , When I write this article , Zhijing also called me for an interview , The written examination passed smoothly ！

2021/10/23 Two rounds of interviews passed successfully , Wait only offer, I feel that I didn't answer well in several places during the interview , The first is that there is a simple concept , Just forget , So I don't know how to answer , Then there's another one that doesn't answer well , I found myself lack of research , Rookies continue to refuel ！ I hope readers can also find good jobs ！