[mik4944]

We cannot use if statement it has o be done using switch only

[objectundefined]

When you write a "boolean statement" (i.e.: the contents of an "if" statement) outside of an "if" statement, it returns either true or false.

Your boolean statement is as follows:

(num < 0)

This can become the target of your switch like so:

switch(num < 0) {
case true:
    alert('NUMBER IS NEGATIVE');
break
case false:
    alert('NUMBER IS POSITIVE OR ZERO');
break
}