Help in autocompleting a sentence in a text field

[RatMomma]

I'm trying to make a piece of javascript code that can read what's on the text field, and then auto complete to a much longer sentence.
So instead of typing in "Delivery Service, #555-6295" I would type in "D" and it would change itself to the full sentence but I'm having trouble figuring out how to do this.
Currently this is my code

Would anybody be able to help?
Thank you

[Nesa Nurani · Accepted solution]

Is it only "D" or it can be "d" too?

Try this as custom keystroke script:

if(event.change == "D")
event.change = "Delivery Service, #555-6295";

[RatMomma]

That works beautifully! Thank you!
This should work fine, but would it be possible to make it a 2 letter keystroke?
I.E.
if(event.change == "DS")
event.change = "Delivery Service, #555-6295";
?
That way if something else needs to be entered starting with the letter D it won't autofill it?

[try67]

No. The change is usually only one letter, unless you paste "DS" into the field, or type very quickly.

[RatMomma]

Thank you very much!