forEach(f) {
    const array = this.array_;
    for (let i = 0, ii = array.length; i < ii; ++i) {
      f(array[i], i, array);
    }
  }
Iterate over each element, calling the provided callback.
@param {function(T, number, Array<T>): *} f The function to call
    for every element. This function takes 3 arguments (the element, the
    index and the array). The return value is ignored.
@api