Node circular dependencies example

car.js

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

var speed = 0;

exports.drive = function () {
	gas.burn();
};

exports.accelerate = function () {
	speed += 10;
	console.log('Car is going: ' + speed);
};

gas.js

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

console.log('Car module (incomplete):', car);

// If I try to invoke "car.accelerate()" here, that method is not yet defined and it will error!
// This is what you want to avoid - directly using another dependency in the high-level code that
// runs while this module itself is being defined.
//
// Uncomment this line and see yourself:
//car.accelerate();

exports.burn = function () {
	// But invoking "car.accelerate()" in here is fine.  By the time
	// the code inside this function is running, car.accelerate()
	// will be defined.
	console.log('Car module (complete):', car);
	car.accelerate();
};

main.js

var car = require('./car');
car.drive();