The most practical use not mentioned here is probably to import existing trained models/weights. I can see it being useful for anything that you want to run in real-time (e.g., webcams apps like https://github.com/ModelDepot/tfjs-yolo-tiny) and can't pay a round-trip cost to server.
Training a model in the browser is the least practical use for tensorflow.js IMO (unless maybe you want to hijack people's browsers to help with training or something).
> Training a model in the browser is the least practical use for tensorflow.js
Unless you want to do some type of federated training in real time without sending private information to the servers (very unusual case in my opinion)
https://js.tensorflow.org/tutorials/import-keras.html
Training a model in the browser is the least practical use for tensorflow.js IMO (unless maybe you want to hijack people's browsers to help with training or something).