simple maybe functor

maybe_functor.ts

class Maybe<T> {
    constructor(private val: T | null|undefined) { }
    public get hasVal():boolean {
        return (this.val !== null || this.val !== undefined);
    }
    public value(fallback: T):T {
        return this.hasVal ? this.val : fallback;
    }
    public map<U>(func:(t: T) => U): Maybe<U> {
        return this.hasVal
            ? new Maybe(func(this.val))
            : new Maybe<U>(null);
    }
}