Concatenate two (or n) streams

This can be done with vanilla Node.js

import { PassThrough } from 'stream'
const merge = (...streams) => {
    let pass = new PassThrough()
    for (let stream of streams) {
        const end = stream == streams.at(-1);
        pass = stream.pipe(pass, { end })
    }
    return pass
}

Use streams.slice(-1)[0] if you don’t have .at() in your version of Node.js