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

Solution

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)

Comments

[loganfsmyth]

It's a rest not a spread FYI, and it's not an operator, it's just syntax.

[Bergi]

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;

[Pranav C Balan]

@bergi is l get defined just before assigning value into b???

[Bergi]

Yes, it's evaluated strictly left-to-right

[Pranav C Balan]

@bergi thanks, now it's clear to me :)

[codeBelt]

const { 0: first, [array.length - 1]: last, ...middle } = array; ____________________________________________________________‌​____________ console.log(first, Object.values(middle), last);