.reduce Math

<!DOCTYPE html>
<html>

  <head>
    <script data-require="immutable.js@*" data-semver="3.7.6" src="https://cdnjs.cloudflare.com/ajax/libs/immutable/3.7.6/immutable.min.js"></script>
  </head>
  <body>
    <script src="script.js"></script>
  </body>

</html>

// make console.log write to the page for better in-browser experience
(function () {
  var body = document.querySelector('body');
  body.style['fontFamily'] = 'monospace';
  body.style['fontSize'] = '2em';
  console.log = function (x) { body.innerText += x + '\n'; };
}());

///////////////////////////////////////////////////////////


let cart = Immutable.fromJS({
  'items': [
    {
      'ASIN': 'B0008KLVVO',   
      'title': 'Paid in Full',
      'price': 4.99
    },
    {
      'ASIN': 'B00HAPTX42',
      'title': 'Hello Nasty',
      'price': 7.00
    }
  ]
})
/**
const subtotal = cart.get('items').reduce((prev, curr, index) => {
  console.log(`prev: ${prev}`)
  console.log(`item ${index} price: ${curr.get('price')}`)
  console.log(`subtotal: ${prev + curr.get('price')}`)
  
  return prev += curr.get('price')
}, 0)
*/

const subtotal = cart.get('items').reduce((t, i) => t += i.get('price'), 0)
console.log(subtotal)

/* Styles go here */