/f(((-|+)?[0-9]\.[0-9]*(-|+)?E[0-9]+)|NaN|+INFIN|-INFIN)e/ (case-sensitive regular expression). NaN, +INFIN and -INFIN denote the real number extensions Not a Number, positive Infinity, negative Infinity as specified by the standard IEEE 754 . The numbers used shouldn't exceed the double precision ranges as specified by IEEE 754, if they do it is at the interpreting clients discretion