1. NodeJs installation

You can visit the NodeJs website to download the latest installation package and install it directly.

NodeJs official website: https://nodejs.org/en/

NodeJs: http://nodejs.cn/

This side contains the latest version and stable version, you can choose to install.

After the installation is complete, enter the command

> node -v
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or

> npm -v
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Check whether the command is available. If the output version is normal, the installation is ok.

2. Common NPM and node commands

NPM common commands

> Output the current version of NPM
> npm -v
> Upgrade the current NPM
> npm install -g npm
> Install partial modules
> npm install
> Install the global module
> npm install -g xxx
> Run the script command
> npm run xxx
> # Display all command information
> npm -l
> ...
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Common Node Commands

> Execute the js file
> node xxx.js
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3, in NodejshttpThe module

Development recommended direct useVSCodeDevelop. You are advised to install plug-in modulesnode-snippets.So let’s just create onejsFile. The inputnodeAfter that, it will automatically prompt youhttp-http-server, select Enter, you can see the following quick creationhttpRequest code. 😄, there is no comment provided by default, I have added a comment here for ease of understanding.

// Introduce the HTTP module
var http = require('http');
/** * request: the server requests information, such as parameters input from the user */ Response: the server responds to the information, which can be set back to the user */
http.createServer(function (request, response) {
  /**
   * 设置请求头信息
   * code（statusCode）： 200
   * headers信息: Content-Type
   */ 
  response.writeHead(200, {'Content-Type': 'text/plain; charset=utf8'});
   // Set the message to be returned
  response.write('Hello World');
  // Tell the client that the request is over
  response.end();
})
// Request listening on port 8081
.listen(8081);

console.log('Server running at http://127.0.0.1:8081/);
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Run the code

> node .\nodejs_http.js
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After running, you can see the log output

Server running at http:/ / 127.0.0.1:8081 /
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Direct browser access, you can see the outputThe above is just a very simple request return, in real use, must be passed parameters, and then returned. Let’s look at how to pass and receive parameters.

Or the example above, the simplest direct GET request, concatenated with one parameter? The username = zhangsan&age = 22.

http://127.0.0.1:8081/?username=zhangsan&age=22
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As mentioned earlier, the request parameter is used to fetch parameters from the client, so let’s print it out first.

console.log(request.url)
// Log output/? username=zhangsan&age=21
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You can see that the request parameters are output normally. The following is to parse to get the parameter, parameter parsing requires the user another module url.

4, nodejsurlThe module

First, introduce the URL module

// Place it directly above the import HTTP module
var url = require('url');
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Parse (request. Url) by adding a line to request

console.log(url.parse(request.url, true))  ParseQueryString =true
// Parse queryString into objects.
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Let’s take a look at the print, focusing on queryString.

Url {
  protocol: null.slashes: null.auth: null.host: null.port: null.hostname: null.hash: null.search: '? username=zhangsan&age=21'.//*** focus on here
  query: [Object: null prototype] { username: 'zhangsan'.age: '21' },
  pathname: '/'.path: '/? username=zhangsan&age=21'.href: '/? username=zhangsan&age=21'
}
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This time, we will parse the received username and age from the request and return them to the client in the form of JSON. At present, the design is to separate the front end from the back end, so it is common to directly return an interface form, so we simulate the return interface form here.

 // Since a normal request is requested twice, once is a normal request and once is favicon.icon, this is filtered out
 if(request.url ! ='/favicon.ico') {// Use url.parse to parse the requested queryString, set to true,
     // Translates queryString directly to a JSON object
     let queryUrl = url.parse(request.url, true).query
     // Construct a JSON return value
     let responseResult = {
         code: 0.message: 'Request successful'.data: {
             username: queryUrl.username,
             age: queryUrl.age
         }
     }
     // Set the return information, where the result is returned to the client as json
     response.write(JSON.stringify(responseResult));
 }
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Refresh the browser again and look at the browser output

At this point, a simple request and return data operation is complete.