Text hint in fillable form

Hi. I've got a problem. I'm looking for a way to make a two different font styles in one box. I managed to make a fillable form that has a default text like:

[  company name ]

when the user writes down his company's name the text disappears, or when he clears his data, the default text is back. That works fine

What I try to do is to make a default text in italic style, while the user written text would be in bold style.

Is it possible to achieve through some Java script? To make two different font styles in one box?

Thanks in advance 😉