Array.getLast()

💡 Ideas
1

This is a very common use case. I often find myself doing the length - 1 trick:

const myArrayWithLongDescriptiveName = ['red', 'yellow', 'green', 'blue']
const lastItem = myArrayWithLongDescriptiveName[myArrayWithLongDescriptiveName.length - 1]

Proposal

Like Array.pop without mutating the original object

const myArrayWithLongDescriptiveName = ['red', 'yellow', 'green', 'blue']
const lastItem = myArrayWithLongDescriptiveName.getLast() // blue

For symmetry I would also add Array.getFirst equivalent to a non-mutating shift

Thoughs ?

2

This seem to work for me!:

Object.defineProperty(Array.prototype, "first", {
	get() {
		return this[0]
	},
	set(item) {
		return this[0] = item
	}
})

Object.defineProperty(Array.prototype, "last", {
	get() {
		return this[this.length -1]
	},
	set(item) {
		return this[this.length -1] = item
	}
})

const arr = [1, 2, 3, 4]
arr.first = 100
console.log("first: ", arr.first, ", last: ", arr.last)
// first: 100, last: 4
3

There was a proposal to introduce yourArray.last (see here), which was later superceded by the more general purpose yourArray.at() proposal.

This let's you do this to get the last item: yourArray.at(-1)

1 Like
4

And .at(-1) is available in Firefox from today!

3 Likes
5

Just checked on Edge. .at appears to be available here too.

6

The problem is, the .at method is not paired with a .setAt method.
We still need to do array[array.length - 1] = value or array.pop(); array.push(value) to set the last item of the array. Only the dropped .lastItem proposal @theScottyJam mentioned solves the problem.

7

You can also do arr.splice(-1, 1, v), which is from the last item, delete 1 item, and insert v

8

Yea I missed that, but I don’t think it’s the best solution as something like array[array.length - 1] += value cannot be done.

9

@graphemecluster - a += operator wouldn't work with a .lastItem() function either.

10

@theScottyJam
No, in the proposal you mentioned, .lastItem is a property with both getter and setter.

1 Like
11

Oh, whoops, you're right. It's been a while since I looked at it.

1 Like