Empty a field when clicking submit in a stateless form.

Empty a field when clicking submit in a stateless form.

I am trying to null a field on the submission of a stateless form with an alert but it's not working.

if(input.Time_Slot == null)
{
alert "Date slot cannot be empty";
input.Type = null;
input.num = null;
}

Its working on user input of a field.

if(input.Type == "none")
{
alert "Date slot cannot be empty";
input.Type = null;
input.num = null;
input.Time_Slot = null;
}

I also have some fields In other forms that need to be null on submit.