Sort an Array of Objects by Date property in JavaScript

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Borislav Hadzhiev

Mon Feb 21 20224 min read

Sort an Array of Objects by Date property in JavaScript #

To sort an array of objects by date property:

  1. Call the sort() method on the array, passing it a function.
  2. The function will be called with 2 objects from the array.
  3. Subtract the date in the second object from the date in the first and return the result.
index.js
const arr1 = [ {id: 3, date: new Date(2022, 1, 24)}, {id: 5, date: new Date(2027, 1, 24)}, {id: 2, date: new Date(2023, 1, 24)}, ]; // ✅ Sort in Ascending order (low to high) const sortedAsc = arr1.sort( (objA, objB) => Number(objA.date) - Number(objB.date), ); // 👇️ {id: 3, date: Thu Feb 24 2022, // id: 2, date: Fri Feb 24 2023 // id: 5, date: Wed Feb 24 2027} console.log(sortedAsc); // ✅ Sort in Descending order (high to low) const sortedDesc = arr1.sort( (objA, objB) => Number(objB.date) - Number(objA.date), ); // 👇️ {id: 5, date: Wed Feb 24 2027, // id: 2, date: Fri Feb 24 2023, // ️ id: 3, date: Thu Feb 24 2022} console.log(sortedDesc);
The code snippet above assumes that your array of objects contains Date objects. If you have Date strings instead, use the map method to convert them to Date objects before calling sort().
index.js
const arr1 = [ {id: 3, date: '2022-02-24'}, {id: 5, date: '2027-02-24'}, {id: 2, date: '2023-02-24'}, ].map(obj => { return {...obj, date: new Date(obj.date)}; }); console.log(arr1); // ✅ Sort in Ascending order (low to high) const sortedAsc = arr1.sort( (objA, objB) => Number(objA.date) - Number(objB.date), ); // 👇️ {id: 3, date: Thu Feb 24 2022, // id: 2, date: Fri Feb 24 2023 // id: 5, date: Wed Feb 24 2027} console.log(sortedAsc); // ✅ Sort in Descending order (high to low) const sortedDesc = arr1.sort( (objA, objB) => Number(objB.date) - Number(objA.date), ); // 👇️ {id: 5, date: Wed Feb 24 2027, // id: 2, date: Fri Feb 24 2023, // ️ id: 3, date: Thu Feb 24 2022} console.log(sortedDesc);
The code snippet above shows how to sort the array of objects by a date property if your starting point is an array containing objects with a date string, instead of a Date object.

We used the Array.sort method to sort an array of objects by a date property.

Note that the sort() method sorts the elements of the array in place and returns the sorted array. In other words, it mutates the original array.

If you want to sort the array without mutating it, use the spread syntax (...) to create a shallow copy before calling the sort() method.

index.js
const arr1 = [ {id: 3, date: new Date(2022, 1, 24)}, {id: 5, date: new Date(2027, 1, 24)}, {id: 2, date: new Date(2023, 1, 24)}, ]; // ✅ Sort in Ascending order (low to high) const sortedAsc = [...arr1].sort( (objA, objB) => Number(objA.date) - Number(objB.date), ); // 👇️ {id: 3, date: Thu Feb 24 2022, // id: 2, date: Fri Feb 24 2023 // id: 5, date: Wed Feb 24 2027} console.log(sortedAsc);

We used the spread syntax (...) to unpack the values of the array into a new array before calling the sort method.

This is probably what you want to be doing since mutations can be confusing and difficult to track throughout a codebase.

We passed the Date objects to the Number function to get the timestamp of each date.

Under the hood each Date object in JavaScript stores the number of milliseconds elapsed between the 1st of January 1970 00:00:00 and the given date.

index.js
// 👇️ 1645454934750 console.log(Number(new Date()));

You can also be more explicit and use the getTime method to get the timestamp.

index.js
// 👇️ 1645454934750 console.log(new Date().getTime());

The parameter we passed to the sort() method in is a function that defines the sort order.

index.js
const arr1 = [ {id: 3, date: new Date(2022, 1, 24)}, {id: 5, date: new Date(2027, 1, 24)}, {id: 2, date: new Date(2023, 1, 24)}, ]; // ✅ Sort in Ascending order (low to high) const sortedAsc = arr1.sort( (objA, objB) => Number(objA.date) - Number(objB.date), ); // 👇️ {id: 3, date: Thu Feb 24 2022, // id: 2, date: Fri Feb 24 2023 // id: 5, date: Wed Feb 24 2027} console.log(sortedAsc);

The function gets called with 2 of the elements (objects) in the array on each iteration.

The sort() method uses the following logic to sort the elements in the array:

  • If the return value of the compare function is greater than 0, then sort b before a.

  • If the return value of the compare function is less than 0, then sort a before b.

  • If the return value of the compare function is equal to 0, keep the original order of a and b.

To sort the array of objects by date property in descending order, you just have to subtract the timestamp of the first date from the timestamp of the second.

index.js
const arr1 = [ {id: 3, date: new Date(2022, 1, 24)}, {id: 5, date: new Date(2027, 1, 24)}, {id: 2, date: new Date(2023, 1, 24)}, ]; // ✅ Sort in Descending order (high to low) const sortedDesc = arr1.sort( (objA, objB) => Number(objB.date) - Number(objA.date), ); // 👇️ {id: 5, date: Wed Feb 24 2027, // id: 2, date: Fri Feb 24 2023, // ️ id: 3, date: Thu Feb 24 2022} console.log(sortedDesc); // 👇️ 1645454934750 console.log(new Date().getTime());
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