Sorting by array position

This is a nice little JS trick I use quite often, let’s say you got an array of objects such as

const classes = [
  {
    name: 'CS101',
    weekday: 'Friday',
  },
  {
    name: 'CS349F',
    weekday: 'Wednesday',
  },
  {
    name: 'CS377E',
    weekday: 'Tuesday',
  },
  {
    name: 'CS390D',
    weekday: 'Thursday',
  },
  {
    name: 'CS294D',
    weekday: 'Monday',
  },
  {
    name: 'CS294S',
    weekday: 'Friday',
  },
  {
    name: 'CS802',
    weekday: 'Wednesday',
  },
]

and you want to sort it by weekday. What you can do is define your desired order in an array like

const WEEKDAY_ORDER = [
  'Monday',
  'Tuesday',
  'Wednesday',
  'Thursday',
  'Friday',
  'Saturday',
  'Sunday',
]

and then you can use indexOf to sort by array indices:

classes.sort(
  (c1, c2) =>
    WEEKDAY_ORDER.indexOf(c1.weekday) - WEEKDAY_ORDER.indexOf(c2.weekday)
)