An object that track the progress of a series of async actions and support stop and resume

machine.js

function Machine(data, done) {
  let status = 'idle'
  let progress = {
    success: 0,
    fail: 0,
    total: data.length
  }

  function* process(data) {
    for (const rec of data) {
      const stopped = yield new Promise(res => {
        setTimeout(() => res(Math.random() > 0.5))
      }, 200)
      if (stopped) {
        break
      }
    }
    done(progress)
    console.log('done');
  }

  const y = process(data)
  function tick() {
    if (status === 'paused') {
      return
    }
    let val = y.next(status === 'stopped')
    if (!val.done) {
      val.value.then(function (v) {
        if (v) {
          progress.success += 1
        } else {
          progress.fail += 1
        }
        setTimeout(tick)
      })
    }
  }

  return {
    start() {
      status = 'running'
      tick()
    },
    pause() {
      status = 'paused'
    },
    stop() {
      status = 'stopped'
    },
    progress,
  }
}

m = Machine([1,2,3,4,5,6], console.log)
m.start()
setTimeout(() => m.pause(), 700)
setTimeout(() => m.start(), 2000)