Basic Implementation of a Transform (Pass-through) Stream

TransformStream.js

function TransformStream() {
    var readableController,
        writableController,
        readable = new ReadableStream({
            start(controller) {
                readableController = controller;
            },
            cancel(reason) {
                writableController.error(reason);
            }
        }),
        writable = new WritableStream({
            start(controller) {
                writableController = controller;
            },
            write(chunk) {
                readableController.enqueue(chunk);
            },
            close() {
                readableController.close();
            },
            abort(reason) {
                readableController.error(reason);
            }
        });

    return {
        readable: readable,
        readableController: readableController,
        writable: writable,
        writableController: writableController
    };
}