singleton.js

var Model = (function() {
	
	var _fromGetInstance = false;
	var _instance;
	
	function _construct() {
	    if (_fromGetInstance !== true) {
	        throw new Error("must use the getInstance.");
	    }
	    _fromGetInstance = false;
	}
	
	_construct.getInstance = function() {
	    if (_instance) {
	        return _instance;
	    }
	    _fromGetInstance = true;
	    return _instance = new this();
	}
	return _construct;
})();