build-object-example.js

const dayNamesInOrder = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat']
const daysOfTheWeek = dayNamesInOrder.reduce((obj, dayName, index) => {
  obj[dayName] = index
  return obj
}, {})

const studentGradeCache = studentNames.reduce((cache, studentName) => {
  cache[studentName] = lookupStudentGrade(studentName)
  return cache
}, {})

const perfectSquaresMemo = [
  0, 1, 2, 3, 4, 5, 6
].reduce((memo, input) => {
  memo[input] = input * input
  return memo
}, {})