Um método de fábrica para a classe JS

function Ctor(param1, param2, param3) {
this._param1 = param1;
this._param2 = param2;
this._param3 = param3;
}

// Factory method w set parameters
Ctor.create = function(p1, p2, p3) {
return new this(p1, p2, p3);
}

// True factory method
Ctor.factroy = function() {
var instance = Object.create(Ctor.prototype);
return Ctor.apply(instance, arguments) || instance;
}

Uso:

var c = Ctor.create(1, 2, 3);
console
.log('c', c, c.create);
console
.assert(c instanceof Ctor);

var cf = Ctor.factroy(1, 2, 3);
console
.log('cf', cf, cf.create);
console
.assert(cf instanceof Ctor);