Why the script function is not working?

Question

Here, I have defined a function inside script. But, it is not validating the emptiness of the text box. Why?
https://code.sololearn.com/WDp33payfBQa/?ref=app

Answer 1

I think it's working just fine!

Answer 2

I'm using this code, in Eclipse LUNA IDE and also tried in Netbeans.