asp-classic - What does an empty input's value when using POST in asp?

Question

I am using asp (JScript as my language) and working with getting data from a form that is sent using POST.

Specifically, I have a text input and I want to check if it was left empty. When leaving it empty, and including Response.Write(Request.form('opt2Dur')) in the called page, nothing prints (doesn't print null or undefined).

My thought was that it was just an empty string so I included this: Response.Write(Request.form('opt2Dur') === ''), however this printed false.

It will print true if I use Response.Write(Request.form('opt2Dur') == '') (== not ===). What is the true value that I can check against using ===? Or, in this case will it be sufficient to check with just ==?

Thanks for any help.