Creating TypeScript objects dynamically

Following a post regarding creating objects dynamically in TypeScript, I have the following code used as a factory to create an object from its name:

public createComponent(context: Object, componentName: string): ComponentRef<ComponentBase> {
    this.viewContainer.clear();
    var instance = 
        Object.create(context[componentName].prototype); // <-- fails
    let componentFactory =
            this.componentFactoryResolver.resolveComponentFactory(instance);
    return <ComponentRef<ComponentBase>> this.viewContainer.createComponent(componentFactory);
}

I'm not entirely convinced I understand this window[suchAndSuch] syntax: what does it mean? Can't find any documentation for it.

In any event it seems that window[myClassName] is undefined, even though the class in question is defined in the same file. I have looked at the Javascript transpiled from the TypeScript, and the class in question is in scope.

I think.

Help!

-- UPDATE -- I have this code, which is part of an Angular 2 application, that is calling the above method to try to get an instance of a component, injectables and all:

export class CustomUserComponent implements OnChanges {
    @Input() componentType: string;
    @ViewChild(ComponentDirective) componentAnchor: ComponentDirective;
    ref: ComponentRef<GalleriaComponentBase>;

    ngAfterViewInit() {
        this.ref = this.componentAnchor
            .createComponent(window, this.componentType);
    }
}