Yes but I don’t know if it was an hard constrain to prepare the model training in JS directly or not.
So I’ve just pointed also to some python resources for the Keras structured data classification that supersed  the tf .feature_column (TF 1.x) mentioned in these zip/geo tutorials.
Many users just prepare the model/experiments on python and then inference on JS so python is not mutually exclusive to JS.
But if it was end2end TF.js requirements yes you could just prepare your embedding or your bucketized input data directly in JS.