当前位置：网站首页>2. Nodejs -- path (\dirname, \filname), URL URL, querystring module, mime module, various paths (relative paths), web page loading (interview questions *)

__dirname: Return the current module file After the analysis Folder in which ( Catalog ) The absolute path of
Use __dirname Variable to get the full directory name of the directory where the current file is located
__dirname Equate to path.dirname(__filename)

（2）__filename

Is a string , representative At present js Path to file ( Absolute path )

__filename: Return the current module file The absolute path after parsing ,
Use __filename Variable to get the file name with the full absolute path of the current module file

2.url website

Composition of the website : agreement ://ip:port/pathname?querystring#hash

domain name ==>DNS analysis Will resolve the domain name into a ip port

Procedures such as ：

var url=require("url")
var str="http://www.baidu.com/20220728/news/page1/index.html?count=20&maxid=123456"
var obj=url.parse(str)
console.log(obj);

Running results ：

3.querystring modular

（1） querystring It literally means Inquire about character string , Usually yes. http Request the data to be parsed .querystring The module only provides 4 A way .
（2）querystring Parameter resolves to an object
（3）querystring Modules are used to implement URL Conversion between parameter string and parameter object

（1）querystring.parse(str, [sep], [eq], [options])
parse This method is to put a string Deserialization For an object .
querystring.parse(str, [sep], [eq], [options])------ Will a query string Deserialize to an object . You can choose whether to overwrite the default delimiter （'&'） And allocators （'='）.
Case study ：
var querystring=require("querystring")
var obj=querystring.parse("username=jack&count=20&maxid=123456")
console.log(obj)
Running results ：

（2）querystring.stringify(obj, [sep], [eq])
------ Serialize an object to a query string.
　　 You can choose whether to overwrite the default delimiter （'&'） And allocators （'='）.　
give an example ：
var querystring=require("querystring")
var str2=querystring.stringify({name:"jack",age:20})
var str3=JSON.stringify({name:"jack",age:20})
console.log(str2);
console.log(str3);
Running results ：
　　　　　　　　　　

4.mime modular

mime It's an Internet standard , By setting it, you can set the opening mode of the file in the browser

（1）mime.getExtension（） You can return the resource type through the path
give an example ：
var mime=require("mime")
var re=mime.getExtension("text/css")
console.log(re)
Running results ：
（2） mime.getType（） You can return the resource type through the path
give an example ：
var mime=require("mime")
var re2=mime.getType("htpp://2342354345:8080/css/sadfsdgfdfg.ttf")
console.log(re2)
Running results ：

5. All kinds of paths ( Relative paths )

（1） Local relative path
for example ： Write the path in the page : file://x1/x2/x2/index.html
"./src/18.jpg" The page of the file that writes this path is opened locally ==> file://x1/x2/x2/src/18.jpg
"src/18.jpg" The page of the file that writes this path is opened locally ==> file://x1/x2/x2/src/18.jpg
"file://c:/"

（2） Local absolute path
Write the path from the root drive letter
for example ："C:/Windows/ASUS/Shortcuts"

（3） Relative network path
for example ：
         The URL of the current page : " agreement ://ip:port /src/news/index.html querystring hash"
         Path inside the page :
                 "./src/18.jpg" ==> " agreement ://ip:port /src/news/src/18.jpg"
                "src/18.jpg" ==> " agreement ://ip:port /src/news/src/18.jpg"
reflection 1:
         User input web address :"http://192.168.6.60:8080/user/20220728/newspage.html?n=20"
         Opened a page , In this page, there is a img Of src yes : "./src/18.jpg"
         Excuse me, 192.168.6.60:8080 This server will be affected req.url What is it? ?
answer : "/user/20220728/src/18.jpg"
reflection 2:
         User input web address :"http://192.168.6.60:8080/user/20220728/newspage"
         Opened a page , In this page, there is a img Of src yes : "./src/18.jpg"
         Excuse me, 192.168.6.60:8080 This server will be affected req.url What is it? ?
answer : "/user/20220728/src/18.jpg"
Its real website :"http://192.168.6.60:8080/user/20220728/src/18.jpg"

（4） Absolute network path
" agreement ://ip:port /src/news/src/18.jpg"
Fallible thinking :
         User input web address : http://192.168.6.60:8080/user/20220728/newspage
         Opened a page , In this page, there is a img Of src yes : "192.168.6.60:8080/src/18.jpg"
         Excuse me, 192.168.6.60:8080 This server will be affected req.url What is it? ?
answer : "/user/20220728/192.168.6.60:8080/src/18.jpg"
Its real website :"http://192.168.6.60:8080/user/20220728/192.168.6.60:8080/src/18.jpg"

（5） Local relative root path
reflection : The user opens locally : "file:///c:/xx/xx2/index.html"
There's a... In the page img Of src yes : "/src/18.jpg"
Its real path :"file:///c:/src/18.jpg"

（6） Network relative root path
reflection :
User input web address : http://192.168.6.60:8080/user/20220728/newspage
Opened a page , In this page, there is a img Of src yes : "/src/18.jpg"
Excuse me, 192.168.6.60:8080 This server will be affected req.url What is it? ?
answer :"/src/18.jpg"
Its real website :"http://192.168.6.60:8080/src/18.jpg"

6. Loading of web pages ( Interview questions *)

1. How do browsers load web pages ？
==>
（1.1） Browser address bar , Enter url , Knock back , Will request a server , The server will return a packet , Is the web code (html Document format ).
（1.2） The browser starts to run parsing html Text ( There is no external picture at this time ,js,css, Font library resources )
        （1.2.1） When parsing , Yes img Labeled src attribute , It will be asynchronous , Start network request server again , The server returns packets ( Picture coding ) Then render it
        （1.2.2） When parsing , Yes link-href It will be asynchronous , Start network request server again , The server returns packets (css code ), Then load .
        （1.2.3） When parsing ,xxxx-url It will be asynchronous , Start network request server again , The server returns packets ( Corresponding code ) Then load .
        （1.2.4） When parsing ,script-src It will be asynchronous , Start network request server again , The server returns packets (js code ), And then use js The engine executes the coding .
（1.3 ） All resources are loaded , Will trigger window.onload

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