Asynchronous Map function extension for the Array interface

arrayMapAsync.ts

interface Array<T> {
    mapAsync<U>(callbackfn: (value: T, index: number, array: T[]) => Promise<U>, thisArg?: any): Promise<U[]>;
}

Array.prototype.mapAsync = function<U>(callbackfn: (value: any, index: number, array: any[]) => Promise<U>, thisArg?: any): Promise<U[]> {
    var promises = this.map((value: any, index: number, array: any[]) => callbackfn(value, index, array));
    return Promise.all(promises);
}