Converting a simple array to object

Question

var arr = [ 'key', 'value' ];
console.log(arr);

var obj = { arr[0] : arr[1] };
console.log(obj);

I'm getting an error doing this array to object conversion. However, this isn't a problem:

var arr = [ 'key', 'value' ];
var key = arr[0];
var value = arr[1];

var obj = { key : value };
console.log(obj);

Why doesn't the array substitution work? What am I doing wrong?

Possible duplicate of How to use a variable for a key in a JavaScript object literal? — Jacob Goh
– Jacob Goh, Commented Jun 20, 2018 at 3:01
The second version is equally problematic. The property's key will be key, not the value you get from the array. Should be var obj = { [key] : value }; — Robby Cornelissen
– Robby Cornelissen, Commented Jun 20, 2018 at 3:05

Inus Saha · Accepted Answer · 2018-06-20 03:00:55Z

8

var arr = [ 'key', 'value' ];
console.log(arr);

var obj = { [arr[0]] : arr[1] };
console.log(obj);

I think the problem is in the key part. have a look how i did it.

answered Jun 20, 2018 at 3:00

Inus Saha

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2 Comments

Hassaanz Over a year ago

this is a very confusing syntax. Would you mind changing your answer so that the code is a bit more declarative? In my opinion, something like: var obj = {}; obj[arr[0]] = arr[1]; Would be easier to understand.

Inus Saha Over a year ago

the person who asked this question has very good reputation. so i posted this answer keeping in mind that he must be an expert. but sure your way is also perfect. meanwhile someone has posted a link of possible duplicate where your answer is also mentioned.

Nina Scholz · Accepted Answer · 2018-06-20 06:57:00Z

2

You need a computed property name for an object literal.

{ [key]: value }
  ^^^^^           left hand side brackets, takes value of key

answered Jun 20, 2018 at 6:57

Nina Scholz

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