How to sort date array in JavaScript

Sorting arrays of dates is a common task in JavaScript. This tutorial shows how to sort an array containing date strings in ascending chronological order.

Suppose we have an array that contains some dates like this:

const arr = [
    [ '02/13/2015', 0.096 ],
    [ '11/15/2013', 0.189 ],
    [ '05/15/2014', 0.11 ],
    [ '12/13/2013', 0.1285 ],
    [ '01/15/2013', 0.12 ],
    [ '01/15/2014', 0.11 ],
    [ '02/14/2014', 0.11 ],
    [ '03/14/2014', 0.11 ]
];

console.log("Original array:");
console.log(arr.slice(0, 4)); // Show first 4 items

Original array:
[
  [ '02/13/2015', 0.096 ],
  [ '11/15/2013', 0.189 ],
  [ '05/15/2014', 0.11 ],
  [ '12/13/2013', 0.1285 ]
]

We need to sort this array in ascending order according to the dates in each sub-array.

Using Array.sort() with Date Comparison

The Array.sort() method with a custom comparator function can sort dates by converting them to Date objects:

const arr = [
    [ '02/13/2015', 0.096 ],
    [ '11/15/2013', 0.189 ],
    [ '05/15/2014', 0.11 ],
    [ '12/13/2013', 0.1285 ],
    [ '01/15/2013', 0.12 ],
    [ '01/15/2014', 0.11 ],
    [ '02/14/2014', 0.11 ],
    [ '03/14/2014', 0.11 ]
];

const sortByDate = arr => {
    const sorter = (a, b) => {
        return new Date(a[0]) - new Date(b[0]);
    };
    arr.sort(sorter);
};

sortByDate(arr);
console.log("Sorted array:");
console.log(arr);

Sorted array:
[
  [ '01/15/2013', 0.12 ],
  [ '11/15/2013', 0.189 ],
  [ '12/13/2013', 0.1285 ],
  [ '01/15/2014', 0.11 ],
  [ '02/14/2014', 0.11 ],
  [ '03/14/2014', 0.11 ],
  [ '05/15/2014', 0.11 ],
  [ '02/13/2015', 0.096 ]
]

How It Works

The sorting function works by:

• Date Conversion: new Date(a[0]) converts the string to a Date object
• Numeric Subtraction: Subtracting Date objects returns milliseconds difference
• Comparison: Negative result means first date is earlier, positive means later

Alternative: One-liner Approach

You can also write this more concisely:

const dates = [
    [ '12/25/2023', 'Christmas' ],
    [ '01/01/2023', 'New Year' ],
    [ '07/04/2023', 'Independence Day' ]
];

const sorted = dates.sort((a, b) => new Date(a[0]) - new Date(b[0]));

console.log(sorted);

[
  [ '01/01/2023', 'New Year' ],
  [ '07/04/2023', 'Independence Day' ],
  [ '12/25/2023', 'Christmas' ]
]

Key Points

• Array.sort() modifies the original array
• Date strings must be in a format recognizable by the Date constructor
• For descending order, reverse the subtraction: new Date(b[0]) - new Date(a[0])

Conclusion

Sorting date arrays in JavaScript is straightforward using Array.sort() with Date object comparison. The key is converting date strings to Date objects for proper chronological sorting.