Get first and last elements in array, ES6 way

Question

let array = [1,2,3,4,5,6,7,8,9,0]

Documentation is something like this

[first, ...rest] = array will output 1 and the rest of array

Now is there a way to take only the first and the last element 1 & 0 with Destructuring

ex: [first, ...middle, last] = array

I know how to take the first and last elements the other way but I was wondering if it is possible with es6

I think this is a duplicate of https://stackoverflow.com/questions/33064377/destructuring-to-get-the-last-element-of-an-array-in-es6 — Amous, Jun 13 '17 at 17:16
**First:** `[first] = [ 1, 2, 3, 4 ].slice(0, 1)`. **Last:** `[last] = [ 1, 2, 3, 4 ].slice(-1)` — Joshua Pinter, Sep 23 '18 at 19:18

Pranav C Balan · Accepted Answer · 2018-04-03T13:28:03.220

48

The rest parameter can only use at the end not anywhere else in the destructuring so it won't work as you expected.

Instead, you can destructor certain properties(an array is also an object in JS), for example, 0 for first and index of the last element for last.

let array = [1,2,3,4,5,6,7,8,9,0]

let {0 : a ,[array.length - 1] : b} = array;
console.log(a, b)

Or its better way to extract length as an another variable and get last value based on that ( suggested by @Bergi) , it would work even there is no variable which refers the array.

let {0 : a ,length : l, [l - 1] : b} = [1,2,3,4,5,6,7,8,9,0];
console.log(a, b)

edited Apr 03 '18 at 13:28

answered Jun 13 '17 at 17:21

Pranav C Balan

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4

It's a rest not a spread FYI, and it's not an operator, it's just syntax. – loganfsmyth Jun 13 '17 at 19:35
3

Uh, yeah, but don't do that. `let a = array[0], b = array[array.length-1];` is just so much cleaner. If we really wanted to make it as concise as possible, there's also `let {0:a, length:l, [l-1]:b} = array;` – Bergi Jun 13 '17 at 20:47
@bergi is `l` get defined just before assigning value into b??? – Pranav C Balan Jun 14 '17 at 02:25
1

Yes, it's evaluated strictly left-to-right – Bergi Jun 14 '17 at 02:37
@bergi thanks, now it's clear to me :) – Pranav C Balan Jun 14 '17 at 03:24
`const { 0: first, [array.length - 1]: last, ...middle } = array;` ________________________________________________________________________ `console.log(first, Object.values(middle), last);` – codeBelt Dec 31 '21 at 20:46

Get first and last elements in array, ES6 way

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