old_contents: console.log('Hello world!');
  
new_contents: import {calculateSavings} from './utils/fuelSavingsCalculator';
  
  function getById(id) {
    return global.document.getElementById(id);
  }
  
  const newMpg = getById('new-mpg');
  const tradeMpg = getById('trade-mpg');
  const ppg = getById('ppg');
  const milesDriven = getById('miles-driven');
  
  const settings = {
    newMpg: newMpg.value,
    tradeMpg: tradeMpg.value,
    ppg: ppg.value,
    milesDriven: milesDriven.value
  };
  
  newMpg.onchange = (e) => {
    settings.newMpg = e.srcElement.value;
    calculateSavings(settings);
  };
  
  tradeMpg.onchange = (e) => {
    settings.tradeMpg = e.srcElement.value;
    calculateSavings(settings);
  };
  
  ppg.onchange = (e) => {
    settings.ppg = e.srcElement.value;
    calculateSavings(settings);
  };
  
  milesDriven.onchange = (e) => {
    settings.milesDriven = e.srcElement.value;
    calculateSavings(settings);
  };
  
  // let inputs = document.getElementsByTagName('input');
  // inputs.map(function(input) {
  //   input.addEventListener("change", function() {
  //     alert('hi');
  //   });
  // });
  
  
subject: Add fuelsavingsform logic