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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.
Otherwise, it'll all just depend on what your intended output. Check out something like https://github.com/bbc/VideoContext for starters or just play around with animating a HTMLCanvasElement and recording its output with HTMLCanvasElement.captureStream().
https://github.com/ffmpegwasm/ffmpeg.wasm is a good place to start, because it'll essentially do anything FFmpeg would do locally (https://github.com/fluent-ffmpeg/node-fluent-ffmpeg is a great Node.js client).