How to implement api for a web application in js and node.js?

Question

JavaScript

I googled, but I didn’t find anything for my task.
In general, there is an application consisting of a layout, a js file and a small server part on node.js. There, the user configures everything for himself through the admin panel and can insert all this customized application to his site.
The layout consists, of course, of a bunch of blocks and all this, how can it be inserted on someone else's site in one block, as it is implemented in all apis, in the form with the subsequent loading of all this stuff through one function in JS?

Answer 1

iframes + js that this iframe creates.

Answer 2

look in the direction of sails.js there is a fullrest api out of the box, the api immediately has built-in methods like create, update, find, delete, etc., you can add your own or disable blocking already built-in ones.