Node.js is light-weight and comes with built-in modules (core modules) for basic tasks like file i/o, networking etc. Some of the useful core modules available with Node.js are
| Core Module Name | Description |
|---|---|
| http | HTTP Server |
| os | Operating System |
| fs | File I/O |
| url | URL Resolution and Parsing |
| path | File and Directory paths |
| net | Networking |
| dns | DNS lookup |
| events | Event Emitters and Listeners |
| stream | Interface for streaming data |
To include a core module in your program, you need to import it using require() function
var x = require('module_name');
Example:
var http = require('http');
var fs = require('fs');
Now we can look at some code samples using core modules.
var os = require("os");
// OS platform
console.log('OS Platform : ' + os.platform());
The above code imports os module and uses the os.platform() method to display the OS Platform.
var fs = require("fs");
fs.stat('samplefolder', function (err, stats) {
if (err) {
console.log("Error");
}
else {
if(stats.isDirectory())
console.log("Directory");
else
console.log("Not a Directory");
}
});
The above code imports fs module. The fs.stat(path, callback) method takes two arguments – the path to the file or directory and a callback function. Since fs.stat() is an asynchronous function, you have to pass a callback function to be executed when it finishes. The callback takes two arguments – err and stats which will be set by the fs.stat() method. The stats object has a stats.isDirectory() method that can be used to check for directories.
Most basic tasks can be performed by using just the core modules. For more advanced tasks, you can use a third-party module or write your own. Many frameworks are also available for rapid development like Express.js, Meteor, Hapi.js, Socket.io
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