Why square brackets allow use of variable value as object key?

Question

code:

const x = 6;
const ob = {x: [6.1, 6.5]} 
console.log(ob) // {x: [6.1, 6.5]}

const y = 6;
const ob = {[y] : [6.1, 6.5]};
console.log(ob) // {6: [6.1, 6.5]}

Why square brackets allow use the value of the variable as object key, is this related to destructuring??

It's a special type of syntax known as computed property names. See: What do square brackets around a property name in an object literal mean? — Nick Parsons
– Nick Parsons, Commented Jul 7, 2020 at 3:46
It's not related to destructuring. In your first example, the two "x"s have nothing to do with each other (the const x line is unused). The syntax ob["foo"] is the same as ob.foo, but you can only use the latter syntax because "foo" is a valid identifier. You could use ob["foo-bar"] but not ob.foo-bar. The bracket syntax also allows you to use a property where you don't know the key at compile time, eg const key = calculateKey();ob[key] — user2740650
– user2740650, Commented Jul 7, 2020 at 3:52

kenput3r · Accepted Answer · 2020-07-07 03:55:22Z

4

The square brackets allow for computed property keys. In other words, the value of the variable inside of the square brackets is processed before the value is accessed.

answered Jul 7, 2020 at 3:55

kenput3r

2492 silver badges10 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Why square brackets allow use of variable value as object key?

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related