Sending data SAP Fiori launchpad webapp/SAPUI5 webapp from client side javascript

This is a general question I have as I am exploring the world of automating some tasks in my workplace.

We have a portal/launchpad environment on our businesses website which has apps shown as tiles.

One of these apps when opened has a homepage that has a bunch of search fields and selectors to interface with (I assume) SAP data.

Ultimately my goal is to be able to send a number to a specific search field on a client-side local webapp (just plain old HTML/jquery stuff) and execute a search for that number in the sapui webapp.

I am getting to an competent level with javascript/HTML/CSS but am completely lost as to where to start with this type of issue as the MVC stuff is completely alien to me.

All my experience has been in creating completely client-side web apps with mostly interface with a local MS Access database.

Is what I am suggesting even possible?

So far I can open the homepage by executing the following code that someone else in the organization used:

window.open('https://fiori.mycompany.com/sap/bc/ui5_ui5/sap/z_cs_ch/index.html

Is it possible to add some form of string after a ?.... at the end of the url?

Again I am completely new to this and looking at the development guides in sapui website isn't shedding any light on it either. Possibly because I don't really know exactly what I am looking for!

Any help /guidance is greatly appreciated.

EDIT: After comments below I can see the request sent to server is in the following format:

Request GET /sap/opu/odata/sap/someotherlocation/SearchTerm('<variable to search for>')?$format=json HTTP/1.1

Am I right in thinking I could potentially send an ajax request to do something similar? If so, how do I go about it?

Thanks again