How to sort an object array by date property?

javascript

prompt-engineering

functions

best-practices

byAlex Kataev·Oct 2, 2024

To sort an array of objects by date property, use Array.prototype.sort() with a lambda expression that subtracts two Date objects. Check out the following snippet sorting in ascending order:

const items = [
  { date: '2022-03-15' },
  { date: '2022-03-14' },
];

// To infinity and beyond!
items.sort((a, b) => new Date(a.date) - new Date(b.date));

Breaking down the sort function

The .sort() function in JavaScript allows for comprehensive sorting. Here are a few aspects to consider:

Uniformity: Ensure all date properties follow the ISO 8601 standard (YYYY-MM-DD) for consistent parsing.
Comparator Shift: Swap the a and b variables inside the comparator for a date-descending sort.
Performance: The efficiency of this method is connected to JavaScript's native sort implementation, giving excellent performance for both large and small datasets.
Neatness: Using an arrow function within the sort function, resulting in more readable and compact comparator function.

Handling edge scenarios

Here is how to conquer potential edge scenarios while sorting dates:

Invalid Dates: Ensure strings are valid dates. If not, assign a default date to prevent parsing errors.
Absent Dates: Some objects might lack a date property. Either filter these out, or assign them a default date.
Time Complexity: In the case of large datasets, look for a sorting algorithm with lower time complexity.

Leveling up: Sorting with orderBy function

Greater sorting complexity might require a custom orderBy function. Here's how you do it:

// Is it an upgrade? Yes, the 'orderBy' upgrade!
if (typeof Array.prototype.orderBy !== 'function') {
  Object.defineProperty(Array.prototype, 'orderBy', {
    enumerable: false,
    writable: true,
    configurable: true,
    
    value: function(priorities) {
      return this.map(item => ({ item, _priorities: priorities(item) }))
                 .sort((a, b) => {
                    for (let i = 0; i < a._priorities.length; i++) {
                      if (a._priorities[i] < b._priorities[i]) return -1;
                      if (a._priorities[i] > b._priorities[i]) return 1;
                    }
                    return 0;
                 })
                 .map(bundle => bundle.item);
    }
  });
}

Using this function, the array can be sorted by descending date, then by ascending name:

const events = ... // populate events
events.orderBy(event => [-(new Date(event.date).getTime()), event.name]);

Ensuring precision with best practices

To maximize accuracy and ensure alignment with best practices:

Convert to Time: For more precise comparisons, convert date strings using new Date(dateString).getTime().
Support: Make the most out of JavaScript's built-in support for comparing dates.
Parse vs Compare: Parse date strings into Date objects for comparison, as directly comparing date strings may yield incorrect results.