DropDown Selection functionality

I’m looking to have a dropdown box that when I select an item a corresponding textfield control gets populated with some default text. For instance I have a drop down that has choices Apple, Banana, Pear. When I select Apply an textfield on the same form gets populated with a fact about Apples. I have set up a workflow but the text only appears when the form is saved and not immediately. Is there a way to accomplish this?

Additionally, I’d like to have a dropdown that I can also type in. My client would like to have prepopulated dropdown of procedures and if they need to slightly alter the procedure they can edit directly in the dropdown field. I get the idea of why this may not be possible but if I could get the item above working then I may be able to direct them to using a slightly different process.

For immediately field filling you must use javascript. Someone with javascript knowledge will be better to answer this.
But why to fill a textfield since you have the dropdown?

Alter on the fly the pre-populated dropdowns… I haven’t seen this before.

Looking to populate the module with predefined data based on a DD selection. Then alter the entries from the ‘template’ as needed.

Can you provide a link to another web app which supports this.

My apologies if my explanation of requirement is over complicating the issue. An example is like most payment or demographic webpages where you start to fill out your name and address and an extension auto fills the rest of the widgets on the form. This is just an example of the intended outcome not a suggestion for implementation as a chrome or google extension isn’t practical in this sense.

For me specifically, I’m working on a project that schedules surgeries, fills out hospital forms, etc. Therefore if I could choose a surgery name from a dropdown and the rest of the surgery module form was filled out with default data it would save a lot of data entry time.

Perhaps there is another workflow I’m not thinking of - Is there a way to save some entries as a template and then instantiate the template for use, without altering the template?

At a simple level it is like the duration field on events. If I choose a start and end time then duration is automatically filled out. I can edit duration and I believe end time is adjusted. I’m looking for similar. I choose something from a drop down and other fields get filled out but I can go back and edit those if needed. So I choose surgery type 1 and I get description , expected medications spinal location, etc. all prepopulated for me. But I can go back and alter the description if needed. It is similar to dynamic dropdowns conceptually.

Thanks so much!