Reduce ES5 / ES6

reduce.js

// reduce boils down a list of values into a single value
//   var callback = function (previousValue, currentValue, index, array) {
//     return previousValue + currentValue    
//   }
//   [].reduce(callback, initialValue)
// 
// Reduce invokes the callback on each item in the array.
// On the first invocation, the first item is passed to the callback as currentValue.
// and the initialValue is passed as the previousValue.
// The returned value of that is then passed into the next invocation of the second item as previousValue. 
// And the currentValue will be the second item.
// 
// 


let items = [["Henry", "Angus Burger", "Water", 13.95, 0.00],
             ["Maggie", "New York Steak", "Diet Coke", 29.95, 1.99],
             ["Anna", "Grilled Salmon", "Water", 17.99, 0.00],
             ["Haylie", "Mac & Cheese", "Orange Juice", 4.95, .99]];

let outputES6 = items.reduce((orders, line) => {
  orders[line[0]] = { entree: line[1],
                      drink: line[2],
                      total: line[3] + line[4] }
  return orders;
}, {});

var outputES5 = items.reduce(function (orders, line) {
  orders[line[0]] = { entree: line[1], 
                      drink: line[2], 
                      total: line[3] + line[4] }
  return orders;
}, {});

console.log(outputES6)
console.log(outputES5)