Update and Post Json body to API from web app

Hi there I would like to post a json body from a web app. The json body will need to be updated by random functions for email address, name, ID etc before it posted via the API. It should be a one click solution which allows for looping. Example: text box with " 5" should send 5 requests to the API. On each execution it should post an updated body. It will also need to output the results on the page afterwards