test-roles.html

<script>

//This is just for the purposes of this test file; in a real application you should use an AMD loader
//such as this: https://github.com/cujojs/curl
var simpleoo;
function define(dependencies, definition) {
	simpleoo = definition();
}

</script>
<script src="simpleoo.js"></script>
<script>

var log = console.log;
var extend = simpleoo.extend;
var mixin = simpleoo.mixin;

function Person() {}

Person.prototype.addRoles = function(role1 /*, role2, ... */) {
	if (this.initRole) {
		throw new Error("addRoles method doesn't work if an initRole method exists on the Person prototype");
	}
	for(var i in arguments) {
		var role = arguments[i];
		if (typeof role.initRole=='function') {
			role.initRole.call(this);
		}		
		mixin(this, role);
	}
	delete this.initRole;
};

var studentRole = {
	initRole: function() {
		console.log('init student');
		this.school = null;
		this.numCourses = null;
	},
	study: function() { log('study'); },
}

var employeeRole = {
	initRole: function() {
		console.log('init employee');
		this.employer = null;
	},
	work: function() { log('work'); }
}

var fred = new Person();
fred.addRoles(studentRole, employeeRole);

fred.school = fred.employer = "Cyberland College";
fred.numCourses = 4;

fred.work();

console.log(fred);

</script>