I made a prototype for the function between . "Why can't I use it directly by number? This is a Number object in general!
var a = 21; 21.between("( 16 20 ]"); // this is wrong and not working //alert ( typeof 21 ) is number a.between("( 16 20 ]"); // working
Try:
(21).between("( 16 20 ]");
When the parser (well, lexer) sees "21." he thinks you have a floating point constant. What also works (and what actually looks disgusting to me personally):
21..between("( 16 20 ]");