bl-test-case.js

const htmlIndex = require('simple-html-index')
const BufferList = require('bl')

function createPage (title) {
  const html = htmlIndex({ title })
  const htmlBuffer = html.pipe(BufferList())

  return function flush () {
    // return htmlBuffer // works
    return htmlBuffer.duplicate() // doesn't work (empty)
  }
}

const page = createPage('Hello')
page().pipe(process.stdout)