description

# deltaY property Null safety

num deltaY

The amount that is expected to scroll vertically, in units determined by deltaMode.

See also:

- WheelEvent.deltaY from the W3C.

## Implementation

    num get deltaY {
      // deltaY may be missing or undefined.
      num? value = JS('', '#.deltaY', this);
      if (value != null) return value;
      throw new UnsupportedError('deltaY is not supported');
    }