Node.js究竟是什么？

1 // jQuery code on the client-side showing how Event-Driven programming works2 ?3 // When a button is pressed, an Event occurs - deal with it4 // directly right here in an anonymous function, where all the5 // necessary variables are present and can be referenced directly6 $("#myButton").click(function(){7 ?????if ($("#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 a10 // connection is made, this particular callback function should be11 // executed. ?Since we‘re creating a web service with REST API,12 // we want an HTTP server, which requires the http variable13 // 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 familiar16 // 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 codes20 ?????// These types of things are handled automatically in server programs21 ?????// like Apache and Tomcat, but Node requires everything to be done yourself22 ?????response.writeHead(200, {"Content-Type": "text/plain"});23 ?24 ?????// Here is some unique-looking code. ?This is how Node retrives25 ?????// parameters passed in from client requests. ?The url module26 ?????// handles all these functions. ?The parse function27 ?????// deconstructs the URL, and places the query key-values in the28 ?????// query object. ?We can find the value for the "number" key29 ?????// 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 create34 ?????// our random number that gets passed back to the caller35 ?????var numInput = new Number(input);36 ?????var numOutput = new Number(Math.random() * numInput).toFixed(0);37 ??????38 ?????// Write the random number to response39 ?????response.write(numOutput);40 ??????41 ?????// Node requires us to explicitly end this connection. ?This is because42 ?????// 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 to47 ???// 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 everything51 // starts up correctly52 console.log("Random Number Generator Running...");