Regular expression: is there a way to set maximum size of pattern?

Question

For example, if I have the string:
0123456789

I would write expresion like this:
0.*9 WHERE PATTERN MAX SIZE is 3. in this case, pattern should fail.

Answer 1

The specific solution to your example is:

/^0.?9$/

The general solution to your abstract question is:

/^(?=.{0,3}$)0.*9$/

In the above (?=.{0,3}$) is a lookahead that the rest of the string has length between 0 and 3.