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SurveyJS
Open-Source JSON Form Builder to Create Dynamic Forms Right in Your App. With SurveyJS form UI libraries, you can build and style forms in a fully-integrated drag & drop form builder, render them in your JS app, and store form submission data in any backend, inc. PHP, ASP.NET Core, and Node.js.
If you are making API calls that are unique or that get you ip banned or rate limited then make them from the frontend if not then from the backend. Also the CORS errors are for security reason and they happen if the call is made from the frontend to a site or API that does not have cors control headers specified. CORS errors can be bypassed with the https://allorigins.win/ API (hacky bypass) if you really need to make the call from the frontend. So be sure to always make calls from the backend if possible.