Module circular dependency weirdness

a.js

var events = require('events');
var b = require('./b');

var emitter = module.exports = new events.EventEmitter();

module.exports.init = function(callback) {
    b.init(function() {
        emitter.emit('done');
    });
};

b.js

var c = require('./c');

module.exports.init = function(callback) {
    c.init(callback);
};

c.js

var a = require('./a');

module.exports.init = function(callback) {
    a.on('ready', function() {
        console.log('"a" is now ready! (from c)');
    });

    callback();
};

main.js

var a = require('./a');

a.on('ready', function() {
    console.log('this a.on was able to be set');
});

a.init(function() {
    console.log('finished main');
});

output

test-circular$ node main.js 

.../test-circular/c.js:5
    a.on('ready', function() {
      ^
TypeError: Object #<Object> has no method 'on'
    at Object.module.exports.init (.../test-circular/c.js:5:7)
    at Object.module.exports.init (.../test-circular/b.js:5:7)
    at EventEmitter.module.exports.init (.../test-circular/a.js:8:7)
    at Object.<anonymous> (.../test-circular/main.js:8:3)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)

Explanation:

The reason this error is happening is not because of a circular dependency. Each module a, b and c gets loaded as you would expect.

The reason c.js does not find the on method is because after c.js stores its reference to a.js, a's module.exports value gets reassigned to new events.EventEmitter(). So it's basically just a shared object reassignment issue.