interface Array<T> {
    /** 
      * Returns the value of the first element in the array where predicate is true, and undefined 
      * otherwise.
      * @param predicate find calls predicate once for each element of the array, in ascending 
      * order, until it finds one where predicate returns true. If such an element is found, find 
      * immediately returns that element value. Otherwise, find returns undefined.
      * @param thisArg If provided, it will be used as the this value for each invocation of 
      * predicate. If it is not provided, undefined is used instead.
      */
    find(predicate: (value: T, index: number, obj: Array<T>) => boolean, thisArg?: any): T;

    /** 
      * Returns the index of the first element in the array where predicate is true, and undefined 
      * otherwise.
      * @param predicate find calls predicate once for each element of the array, in ascending 
      * order, until it finds one where predicate returns true. If such an element is found, find 
      * immediately returns that element value. Otherwise, find returns undefined.
      * @param thisArg If provided, it will be used as the this value for each invocation of 
      * predicate. If it is not provided, undefined is used instead.
      */
    findIndex(predicate: (value: T) => boolean, thisArg?: any): number;

    /**
      * Returns the this object after filling the section identified by start and end with value
      * @param value value to fill array section with
      * @param start index to start filling the array at. If start is negative, it is treated as 
      * length+start where length is the length of the array. 
      * @param end index to stop filling the array at. If end is negative, it is treated as 
      * length+end.
      */
    fill(value: T, start?: number, end?: number): T[];

    /** 
      * Returns the this object after copying a section of the array identified by start and end
      * to the same array starting at position target
      * @param target If target is negative, it is treated as length+target where length is the 
      * length of the array. 
      * @param start If start is negative, it is treated as length+start. If end is negative, it 
      * is treated as length+end.
      * @param end If not specified, length of the this object is used as its default value. 
      */
    copyWithin(target: number, start: number, end?: number): T[];
}

interface ArrayConstructor {
    /**
      * Creates an array from an array-like object.
      * @param arrayLike An array-like object to convert to an array.
      * @param mapfn A mapping function to call on every element of the array.
      * @param thisArg Value of 'this' used to invoke the mapfn.
      */
    from<T, U>(arrayLike: ArrayLike<T>, mapfn: (v: T, k: number) => U, thisArg?: any): Array<U>;


    /**
      * Creates an array from an array-like object.
      * @param arrayLike An array-like object to convert to an array.
      */
    from<T>(arrayLike: ArrayLike<T>): Array<T>;

    /**
      * Returns a new array from a set of elements.
      * @param items A set of elements to include in the new array object.
      */
    of<T>(...items: T[]): Array<T>;
}