TypeScript final and frozen class decorators

example.ts

import { final } from './final.ts';
import { frozen } from './frozen.ts';

@final
@frozen
export class Example {
}

export class ExampleSub extends Example {
}

const isFrozen = Object.isFrozen(Example); // true
new ExampleSub(); // errror thrown

final.ts

/**
 * Prevent instances from inherited classes.
 * @param target Target.
 */
export function final<T extends { new (...args: any[]): object }>(target: T): T {
    return class Final extends target {
        constructor(...args: any[]) {
            if (new.target !== Final) {
                throw new Error('Cannot inherit from final class');
            }
            super(...args);
        }
    };
}

frozen.ts

/**
 * Freeze constructor and prototype.
 * @param target Target.
 */
export function frozen(target: Function): void {
    Object.freeze(target);
    Object.freeze(target.prototype);
}

More info here: http://www.broculos.net/2017/10/typescript-final-class-decorator.html#.WfSiLWhSyUk