This List class re-creates simplified version of standard array functionality.
Returns an array where each item has been transformed according to the callback function. Skips (but preserves) 'holes' in the array.
Returns an array containing only the elements that meet the criteria in the callback.
Returns the index of the first element that meets the criteria in the callback, or -1 if no such element is found.
Returns a single reduced value based on the callback (with or without initial value)
Return false when any element does not meet the criteria in callback. Otherwise (all elements meet the criteria), returns true.