Say you have an array of objects like this, which contains a set of date objects:

const activities = [
  { title: 'Hiking', date: new Date('2019-06-28') },
  { title: 'Shopping', date: new Date('2019-06-10') },
  { title: 'Trekking', date: new Date('2019-06-22') }

You want to sort those activities by the date property.

You can use the sort() method of Array, which takes a callback function, which takes as parameters 2 objects contained in the array (which we call a and b):

const sortedActivities = activities.sort((a, b) => -

When we return a positive value, the function communicates to sort() that the object b takes precedence in sorting over the object a. Returning a negative value will do the opposite.

The sort() method returns a new sorted array, but it also sorts the original array in place. Thus, both the sortedActivities and activities arrays are now sorted. One option to protect the original array from being modified is to use the slice() method to create a copy of the array prior to sorting, as follows:

const sortedActivities = activities.slice().sort((a, b) => -

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