Think API first

index.js

const ChartManager = function() {
  function init() { }

  function config() { }

  function setData() { }

  function render() { }
  
  return {
    init,
    config,
    setData,
    render
  }
}

const DataManager = function() {
  function getData() { }

  function getFilteredData() { }
  
  return {
    getData,
    getFilteredData
  }
}