I want create object factory using ES6 but old-style syntax doesn't work with new.

I have next code:

export class Column {}
export class Sequence {}
export class Checkbox {}

export class ColumnFactory {
    constructor() {
        this.specColumn = {
            __default: 'Column',
            __sequence: 'Sequence',
            __checkbox: 'Checkbox'
        };
    }

    create(name) {
        let className = this.specColumn[name] ? this.specColumn[name] : this.specColumn['__default'];
        return new window[className](name); // this line throw error
    }
}

let factory = new ColumnFactory();
let column = factory.create('userName');

What do I do wrong?