Factory Function in JavaScript

javascript_factory.js

function FactoryFunction() {
    var obj = {
        prop3: 3,
        prop4: 4
    };

    return obj;
}

FactoryFunction.prototype.myMethod = function () { };

//returns Object. myMethod won't be available here
var obj3 = new FactoryFunction(); 

//returns Object. myMethod won't be available here
var obj4 = FactoryFunction();