How do you specify conditional text values using JavaScript?

Hello,

Id like to have a text field in my My LiveCycle form
populate with a specific text value when it is checked (or on),
and have the text field be blank (no text) if the checkbox
is not checked (or off)

Here is basically how I need the script to work:

If checkbox1 is on then textfield1 = "hello"

If checkbox1 = off then textfield1 = blank (no text)

Any help would be greatly appreciated.

Thank you.