class Unit { constructor(){ } } var str = "Unit"; var a = new window[str](); // error var b = new window["Unit"](); // error var u = new Unit(); // works (u instanceof Unit) // true I only recently made the switch to ES 6 syntax in regards to declaring classes. Im pretty sure that formerly i could instantiate a class like this, however ever since i have used "class" syntax, the instantiation of an object by windowclassName is not working anymore.
What exactly am i missing here ?
Variables declared with class behave similarly to those declared with const and let - they do not get implicitly assigned to the window object (which is arguably a good thing). If you wanted to put Unit on window, you would have to do so explicitly:
class Unit { constructor(){ console.log('constructing'); } } window.Unit = Unit; var str = "Unit"; var a = new window[str]();You might consider using your own object of classes to avoid global pollution:
const myClasses = { Unit: class Unit { constructor(){ console.log('constructing'); } } }; var str = "Unit"; var a = new myClasses[str]();Object values cannot reference each other while in the process of declaring an object literal - to put a subclass on myClasses that extends one of the existing classes, you'll have to do so outside of the myClasses declaration:
const myClasses = { Unit: class Unit { constructor(){ console.log('constructing'); } } }; myClasses.Child = class Child extends myClasses.Unit { constructor() { super(); console.log('Child running'); } } var str = "Child"; var a = new myClasses[str]();
myClasses object has finished being made.