How can i check if variable exist

Scripting
1

How can I check if variable is set already ?

2

we need to see some code. there are many ways of checking things. and what do you mean by is set?

is this set or not set? it could be both. depends on the code and what it means in the code.
public int someInt = 0;

but an if statement is an easy way to check things.

if(someInt != 0)
{
//it is set, do some thing
}else
{
//not set, do nothing
}