How to verify that the input box is non-null?

How to verify that the input box is non-null?
The input box has been automatically filled with values, and the check input box is not empty.
(upload://ebEEb3gwL5ZgSge39jXdkMH8zyF.png)

Can you share a screenshot of the HTML for the elements in question? elements come in many shapes and forms, so checking for “non-null” can have various implementations.