On the brain.js page there is a simple example of LSTMTimeStep - https://github.com/BrainJS/brain.js
var net = new brain.recurrent.LSTMTimeStep();
net.train(
You need to train with given sets and then if you want you can do following for next 10 items: Predict next item. Add it to training set. Predict next +1 item. Add next +1 to training set.
Also read about the stream on github repo. I also suggest you update your question with what you have tried so far it will help future users to understand the question further and add to both question and answer.