Extending

A.js

var Base = require('./Base');
module.exports = Base.extend({
	
});

B.js

var Base = require('./Base');
module.exports = Base.extend({
	
});

Base.js

var _ = require("underscore");
module.exports = {
	prop: 10,
	extend: function(child) {
		return _.extend({}, this, child);
	},
	changeProp: function(v) {
		this.prop = v;
	},
	getProp: function() {
		return this.prop;
	}
}

console

node ./index.js

outputs: 300 10

index.js

var A = require('./A.js');
var B = require('./B.js');

A.changeProp(300);

console.log(A.getProp(), B.getProp());