What is best practice making custom pages to access multiple tables?

Can someone point me in the right direction

I want to know best practice for creating a custom QB page that gets data from multiple tables and can edit. It will be opened on an Ipad with the QB app.

I don't see any recent libraries to help do this, so I think I'm missing something.
Do most people create a html page with embedded javascript and use ajax to get/update data from tables using get string queries?
Or is it more complex using json api and dom updates.?

is there any tutorials on this? Or any resources that you know of that may help me understand?

thanks

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Johnny Niumata
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