<p>can i somehow compare two numbers in regex?
i want regex that is correct for 10-12, but incorrect for 12-10. I mean that 10 must be smaller than 12.
I want to do it in Javascript.</p>

I wouldn't use regex for this.  I'd split the string on the operator, then compare the two resulting numbers based on what operator I found (I'm assuming
```
10+12
```
and
```
12+10
```
would both be legal).