sample.js

//Get streams
const {readableStream, writableStream} = event.data;
//New transform stream for inserting metadata
const transformStreamMetadata = new TransformStream ({transform: insert});
//New transform stream for encryption
const transformStreamEncrypt = new TransformStream ({transform: encrypt});
//Pipe
readableStream
    .pipeThrough (transformStreamMetadata)
    .pipeThrough (transformStreamEncrypt)
    .pipeTo (writableStream);