A number is very much like a C or Java number, except that the octal and hexadecimal formats are not used. A number is a sequence of decimal digits with no superfluous leading zero.
It may have a preceding minus sign (U+002D). It may have a fractional part prefixed by a decimal point (U+002E). It may have an exponent, prefixed by e (U+0065) or E (U+0045) and optionally + (U+002B) or – (U+002D). The digits are the code points U+0030 through U+0039.
Numeric values that cannot be represented as sequences of digits (such as Infinity and NaN) are not permitted.