export interface Iterator<K,V> {
    (value: V, key: K): void
}

export interface IterableObject <T> {
    [key: string]: T
}

export function forEach <T>(items: IterableObject<T>, func: Iterator<string, T>)
export function forEach <T>(items: T[], func: Iterator<number, T>)
export function forEach (items, func: Iterator<any, any>) {

    let isObject = (typeof items == 'object');
    let isArray = isObject && 'slice' in items;

    if ( !isObject && !isArray ) throw Error(`Items are not iterable`);

    if ( isArray ) {
        for ( let i = 0, length = items.length ; i < length ; i++ )
            func.call(func, items[i], i);
    } else {
        let keys = Object.keys(items);
        for (let i = 0, length = keys.length; i < length; i++)
            func.call(func, items[ keys[i] ], keys[i]);
    }
}