Let’s say you have an an array with a list of awesome wizards.
let wizards = ['Gandalf', 'Merlin', 'Radagast', 'Merlin'];
You’ll notice that
Merlin appears in the list twice. You can get the index of the first instance of
Merlin using the
// returns 1 let index = wizards.indexOf('Merlin');
But what if you wanted to get the index of the last instance of
Merlin in the
wizards array instead? For that, we can use the
Just like with
Array.indexOf(), pass in the item to get as an argument. It returns the index of the last instance of that item, or
-1 if it doesn’t exist.
// returns 3 let lastIndex = wizards.lastIndexOf('Merlin');
If there’s only one instance of an item, it still works.
// returns 0 let gandalf = wizards.lastIndexOf('Gandalf');