Nodejs creates web server hello world program_javascript skills

The main application of Node.js is server programming.

One of the main purposes of designing Node.js is to provide a highly scalable server environment. This is the difference between the Node and V8 engines we introduced at the beginning of this chapter. In addition to using the V8 engine to parse JavaScript, Node also provides highly optimized application libraries to improve server efficiency. For example, the HTTP module was rewritten in C specifically for a fast, non-blocking HTTP server. Let’s take a look at the classic “Hello World” example of Node using an HTTP server

/*Create server*/

var server=http.createServer(function(req,res){
  res.writeHead(200,{"Content-type":'text/html'});
  res.end('hello world');
});

/*Monitoring IP and port*/

server.listen(8124,'127.0.0.1',function(){
  console.log('服务器创建成成功:127.0.0.1:8124');
});

The running code is as follows

ZXD@ZXD-PC /K/work/learn/nodejs/cvs01
$ node app

Server created successfully: 127.0.0.1:8124

This sample code first includes the HTTP library into the program through the require method. Many languages ​​have this approach of including other libraries, Node uses the CommonJS module style.

What you need to understand now is that the functions of the HTTP library have been assigned to the http object.

Next, we need an HTTP server. Other languages ​​such as PHP need to run in a server like Apache, but Node is different from them because Node itself is a Web server.

But this also means we need to create the server first. The next line of code calls a factory pattern method of the HTTP module
(createServer) to create a new HTTP server. The newly created HTTP server is not assigned to any variables, it will only become an anonymous object that lives in the global scope.

We can initialize the server through chain calls and tell it to listen on port 8124. When calling createServer, we pass an anonymous function as a parameter. This function is bound to the event listener of the newly created server for request event processing. Message events are at the heart of JavaScript and Node. In this example, every time a new access request arrives at the Web server, it will call the function method we specified to handle it. We call this type of method a callback. Because whenever an event occurs, we will call back all functions that listen to this event.

Example 2:

Due to traveling to another city and not having a computer at hand, dom framework cannot be released as scheduled, so take this opportunity to learn something new. The most urgent need during this period was to find an ultra-lightweight backend to set up my framework, so I reached out to the legendary Server-Side Javascrpt. The most famous back-end JS is undoubtedly node.js by Ryan Dahl, and the other is jaxer produced by aptana IDE provider.

First download node.js, then unzip it to the E drive, rename it to node, then enter cmd in the start menu, and use the cd command to switch to the nodejs decompression directory:

First example: hello world.

Create the hello.js file in the node directory, and then enter:

var sys = require("sys"); 
sys.puts("Hello world"); 

Then we enter the command node hello.js in the naming platform, and we can see the naming platform output Hello world.

Second example: hello world2.

Okay, this time we try to output hello world from the browser. Create http.js in the node directory and enter:

var sys = require("sys"), 
  http = require("http"); 
http.createServer(function(request, response) { 
  response.sendHeader(200, {"Content-Type": "text/html"}); 
  response.write("Hello World!"); 
  response.close(); 
}).listen(8080); 
sys.puts("Server running at http://localhost:8080/"); 

Then we enter the command node http.js in the naming platform and http://localhost:8080/

The third example: hello world2.

node.js provides a Buffer class for converting strings of different encodings.

Currently supports three types: 'ascii', 'utf8' and 'binary'. See here for details

var Buffer = require('buffer').Buffer, 
buf = new Buffer(256), 
len = buf.write('\u00bd + \u00bc = \u00be', 0); 
console.log(len + " bytes: " + buf.toString('utf8', 0, len)); 

The fourth example: hello world3.

//synopsis.js 
//synopsis 摘要, 梗概，大纲 
var http = require('http'); 
  
http.createServer(function (request, response) { 
 response.writeHead(200, {'Content-Type': 'text/plain'}); 
 response.end('Hello World\n'); 
}).listen(8124); 
  
console.log('Server running at http://127.0.0.1:8124/');