How does require() in node.js work?

Question

I tried this:

// mod.js var a = 1; this.b = 2; exports.c = 3;  // test.js var mod = require('./mod.js'); console.log(mod.a);    // undefined console.log(mod.b);    // 2 console.log(mod.c);    // 3, so this === exports? 

So I image that require() may be implement like this:

var require = function (file) {     var exports = {};     var run = function (file) {         // include "file" here and run     };     run.apply(exports, [file]);     return exports; } 

Is that right? Please help me to understand require(), or where can I find the source code. Thanks!

Answer 1

Source code is here. exports/require are not keywords, but global variables. Your main script is wrapped before start in a function which has all the globals like require, process etc in its context.

Note that while module.js itself is using require(), that's a different require function, and it is defined in the file called "node.js"

Side effect of above: it's perfectly fine to have "return" statement in the middle of your module (not belonging to any function), effectively "commenting out" rest of the code