Node.js究竟是什么？

1 // jQuery code on the client-side showing how Event-Driven programming works
2  
3 // When a button is pressed, an Event occurs - deal with it
4 // directly right here in an anonymous function, where all the
5 // necessary variables are present and can be referenced directly
6 $("#myButton").click(function(){
7      if ($("#myTextField").val() != $(this).val())
8          alert("Field must match button text");
9 });

 1 // these modules need to be imported in order to use them.
 2 // Node has several modules.  They are like any #include
 3 // or import statement in other languages
 4 var http = require("http");
 5 var url = require("url");
 6  
 7 // The most important line in any Node file.  This function
 8 // does the actual process of creating the server.  Technically,
 9 // Node tells the underlying operating system that whenever a
10 // connection is made, this particular callback function should be
11 // executed.  Since we‘re creating a web service with REST API,
12 // we want an HTTP server, which requires the http variable
13 // we created in the lines above.
14 // Finally, you can see that the callback method receives a ‘request‘
15 // and ‘response‘ object automatically.  This should be familiar
16 // to any PHP or Java programmer.
17 http.createServer(function(request, response) {
18  
19      // The response needs to handle all the headers, and the return codes
20      // These types of things are handled automatically in server programs
21      // like Apache and Tomcat, but Node requires everything to be done yourself
22      response.writeHead(200, {"Content-Type": "text/plain"});
23  
24      // Here is some unique-looking code.  This is how Node retrives
25      // parameters passed in from client requests.  The url module
26      // handles all these functions.  The parse function
27      // deconstructs the URL, and places the query key-values in the
28      // query object.  We can find the value for the "number" key
29      // by referencing it directly - the beauty of JavaScript.
30      var params = url.parse(request.url, true).query;
31      var input = params.number;
32  
33      // These are the generic JavaScript methods that will create
34      // our random number that gets passed back to the caller
35      var numInput = new Number(input);
36      var numOutput = new Number(Math.random() * numInput).toFixed(0);
37       
38      // Write the random number to response
39      response.write(numOutput);
40       
41      // Node requires us to explicitly end this connection.  This is because
42      // Node allows you to keep a connection open and pass data back and forth,
43      // though that advanced topic isn‘t discussed in this article.
44      response.end();
45  
46    // When we create the server, we have to explicitly connect the HTTP server to
47    // a port.  Standard HTTP port is 80, so we‘ll connect it to that one.
48 }).listen(80);
49  
50 // Output a String to the console once the server starts up, letting us know everything
51 // starts up correctly
52 console.log("Random Number Generator Running...");