NodeJs, all kinds of path

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One, local relative path and absolute path

Local relative path:
Simply speaking, this file page is opened locally, and then relative to the path of this file, such as "./" means it is at the same level as this fileYou can also omit "./" and enter the file name directly, and "../" means it is the same level as the parent of this file.

On the ajax1.html page we want to get bilibili-img.png image, the relative path can be filled in "../img/bilibili-img.png"

Local absolute path:
The absolute path is the location of the file on the disk, starting with the disk name; the path where we right-click the file to copy the path is the local absolute path, for example, we want toGet the bilibili-img.png image, right-click and copy the path: G:\H5\dom\app\img\bilibili-img.png This is the absolute path.

Second, relative network path and absolute network path

Relative network path:
The directory path created based on the location of the web page that references the file.Therefore, when web pages saved in different directories refer to the same file, the paths used will be different, so it is called relative.This path is used in the same way as a local relative path, except that the file is opened on the server.
For example:
The user enters the URL:
"http://www.baidu.com/user/login"
A page is opened, and the src of an img in this page is: "./src/baidu.jpg”
What is the req.url that the server www.baidu.com will receive?
Answer: “/user/src/baidu.jpg”
Its real URL:"http://www.baidu.com/user/src/baidu.jpg"

Absolute network path:
The directory path referenced to the root of the web site.The reason why it is called absolute means that when all web pages refer to the same file, the path used is the same.Format: Protocol://ip:port/The location of the file under this server file;
The above picture is an example: when we use the app file as the root directory of the Web site, we need to get the bilibili-img.png picture,The path is:
http or https://local ip: server listening port number or domain name /img/bilibili-img.png
When we want to use pictures on the network, do not download and use them, copy the pathIt is an absolute path:
https://i0.hdslb.com/bfs/archive/7a2a097d57ce0d7c2c46585ff98c45368e7386eb.png

Third, local relative root path and network relative root path

Local relative root path:
When we only enter "/", it is relative to the path in the root directory of the disk where the file is located, for example
There is a path under my G driveImage

The path of the html file I run is G:\H5\dom\app\src\ajax1.html
We only need to fill in "\bilibili.png" when we visit this image

Click me

Click to access

Network relative root path
The fundamental relative root path is similar, the difference is relative to the root directory of the server running this file
For example:
User input URL:http://www.baidu.com/user/newspage
opened a page, in this page there is an img's src: "/src/baidu.jpg"
May I ask www.baidu.com thisWhat is the req.url that the server will receive?
Answer: "/src/baidu.jpg"
Its real URL is: "http://www.baidu.com/src/baidu.jpg"

Fourth, the global variable that displays the path in node.js

The global variable __dirname is a string representing the path of the directory where the current js file is located (absolute path)
The global variable __filename is a string representing the path (absolute path) of the current js file