How to keep the original stream data unchanged?

[ahrtr]

I am using event-stream to process a http request payload. The payload is a JSON stream (new line separated JSON), and I want to extract all the interested fields. The code is something like below,

import JSONStream from 'JSONStream';
import eventStream from 'event-stream';

async function processPayload(request) {
    const payload = request.payload;
    let indexArray = [];
    await eventStream.pipeline(
        payload, 
        JSONStream.parse(['test']),
        eventStream.mapSync(function(data){
            indexArray.push(data);
        })
    );
    return indexArray;
}

Basically the above code works well. But the issue is that it modifies the original payload, so the following operation which depends on the payload as well fails. How can I keep the original data being unchanged? Thanks!

[right9ctrl]

@ahrtr Can you pipe the request payload into two streams? See #12