Figure out if number is a minus or a positive number

Figure out if number is a minus or a positive number

Say I have a range which consists of "< -10" and I split this up using a
regex call which leaves me with '<' '-10'.
I then have a function which gets me the number from the split and I call
it like range1.getMin(), this would return '-10' but when I use
range1.getMin().indexOf('-') it doesn't work.