I don't know how to judge when the value of the field is Infinity.
Is isFinite cannot be used ?
If not, how can I determine it?
Sorry ! It's my other mistake.
isFinite is available.
I want to erase this question but I don't know how to use this site.
My guess is you're dividing by zero.
That is what causing your result to be "Infinity", as it's an illegal operation.