How to take several files from the back and compare their contents with each other with the output of the comparison result to the front?

Question

API

Here is an example of what I need:

At the front there is a search bar that should suggest the names of different sweets. On the back (somewhere) is a database with sweets. And every sweet has a composition.
I need that after selecting two sweets from the search bar, a field appears below that shows all the sweets with the same ingredient from the composition of the file with the sweet. And to show the name of the sweet and its composition.

Difficulties and misunderstandings are:
How to connect to the back (including some access keys, I don't know how this usually happens)?
How to get the necessary files? (Or do they not need to be taken out and they can still be compared on the back?)
How to get only a fragment of each file with an ingredient?
And all this needs to be done through vue

Answer 1

To do all this through vue, you must have an api on the back that will either return the product and its composition on request, or will parse your search string and return all the products from it, or even prepare the entire result on the back and return json , which should just be styled in the front template.
How to connect to the back and all other questions - this is for you to the back developer. No other way.