Trying to build a regular expression to check pattern

Question

a) Start and end with a number
b) Hyphen should start and end with a number
c) Comma should start and end with a number
d) Range of number should be from 1-31

Answer 1

How about this? This will check rules a, b and c, at least, but does not check rule d.

/^[0-9]+(-[0-9]+)?(,[0-9]+(-[0-9]+)?)*$/

If you need to ensure that all the numbers are in the range 1-31, then the expression will get a whole lot uglier:

/^([1-9]|[12][0-9]|3[01])(-([1-9]|[12][0-9]|3[01]))?(,([1-9]|[12][0-9]|3[01])(-([1-9]|[12][0-9]|3[01]))?)*$/

Note that your example c contains a number, 56, that does not fall within the range 1-31, so it will not pass the second expression.