How to get the last matching item in an array with vanilla JavaScript

Last week, I wrote about the Array.prototype.find() method and the Array.prototype.findIndex() method. They find the first item in an array that matches some criteria you specify (or it’s index).

Today, I want to talk about some companion methods that find the last matching item instead. Let’s dig in!

The Array.prototype.findLast() method

Let’s imagine you have an array of todos, and at least one of the items has a duplicate item property.

let todos = [
	{
		item: 'Wash the dog',
		added: 20180322,
		completed: false
	},
	{
		item: 'Launch a podcast',
		added: 20180305,
		completed: false
	},
	{
		item: 'Wash the dog',
		added: 20180222,
		completed: true
	},
];

If you used the Array.prototype.find() method to search for the object with Wash the dog as its item, it would return the first object, added on 20180322 and not completed.

// returns the first item
let washTheDog = todos.find(function (todo) {
	return todo.item === 'Wash the dog';
});

If you instead wanted to find the last matching item, you can use the Array.prototype.findLast() method. It works exactly the same way, but returns the last matching item instead of the first.

This returns the todo that was added on 2018022 and is completed.

// returns the first item
let washTheDog = todos.findLast(function (todo) {
	return todo.item === 'Wash the dog';
});

The Array.prototype.findLastIndex() method

Similarly, the Array.prototype.findLastIndex() method works just like the Array.prototype.findIndex() method, but finds the index of the last matching item instead of the first.

// returns 2
let washIndex = todos.findLastIndex(function (todo) {
	return todo.item === 'Wash the dog';
});