set multiple conditions in ternary operator

I want to set a condition that it should not be greater than 10 or less than 0 but i don't understand how to set in ternary operator

var count = 0;

var res = flag == "1" ? ++count : flag == "0" ? --count;

Each condition is returning a result. Let's try to add some formatting. Your's missing the final else statement for the last condition.

var count = 0;

var res =
  flag == "1"
    ? ++count
    : flag == "0"
      ? --count
      : doSomethingElse

Anyway, based on what you wrote you want your number to be 0-10. We don't use ++ and -- until we sure we want to write the value. If we're out of range, we simply return the original count value.

var res =
  (count + 1) < 10
    ? count++
    : (count - 1 < 0)
      ? count--
      count