code: function loadCallbackBatch () {
    io.load({
      hello: { text: 'assets/hello.txt' },
      color: { json: 'assets/color.json' },
      pex: { image: 'assets/pex.png' },
      data: { binary: 'assets/data.bin' }
    }, (err, res) => {
      if (err) return console.log(err)
      state.callbackBatch.text = res.hello
      state.callbackBatch.json = res.color
      state.callbackBatch.image = res.pex
      state.callbackBatch.binary = res.data
    })
  }
docs: callback batch