Returns the width of any overridden character. Return undefined if not overridden. Return POTENTIAL_EMOJI(14) if this code point might start an emoji sequence, and AMBIGUOUS(15) if this code point point has ambiguous East Asian Width. This is useful if your display context (terminal application + font) renders a particular grapheme cluster differently than mine does.
Override the widths of some characters. This is most easily achieved with a JS Map object.