You want \s
Matches a single white space
character, including space, tab, form
feed, line feed.
Equivalent to
[ \f\n\r\t\v\u00a0\u1680\u2000-\u200a\u2028\u2029\u202f\u205f\u3000\ufeff]
in Firefox and [ \f\n\r\t\v] in IE.
str = str.replace(/\s/g, "X");