TypeScript Keys Helper

gistfile1.txt

type KeysOf<T> = { [x in Exclude<keyof T, keyof KeyHelper<T>>]: null }

abstract class KeyHelper<T> {
    abstract $keys: KeysOf<T>;
    getKeys(): (keyof T)[] {
        return Object.keys(this.$keys) as (keyof T)[];
    }
}

class Greeter extends KeyHelper<Greeter> {

    $keys: KeysOf<Greeter> = {
        greeting: null,
        greet: null,
        who: null,
    }

    who: string;
    greeting: string;
    greet() {
        return "Hello, " + this.greeting;
    }
}

let greeter = new Greeter();

alert(greeter.getKeys().join(", "))