There are six explicitly defined white space characters and a whole Unicode category.
Tab (\u0009), Vertical Tab (\u000B), Form Feed (\u000C), Space (\u0020), No-Breaking Space (\u00A0) and any character in the Unicode Zs category (USP) of the Unicode 3.0 standard, or later.
Note that line terminators such as \u000A are NOT considered white space in Javascript for several reasons. Mostly because their presence might cause an automatic semi-colon insertion to happen.