Javascript object - using array value as key

Question

I have the following array

  const lastThreeYearsArr = [currYear, currYear-1, currYear-2 ]

I need to define an object as:

var obj = {lastThreeYearsArr[0]: 0, lastThreeYearsArr[1]: 0, lastThreeYearsArr[2]: 0};

But using the array as key doesn't seem to work in javascript. Is there a way to access the array value and put it as key in the object.

[Computed property names](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Object_initializer#Computed_property_names) — ASDFGerte, Apr 26 '18 at 15:36

score 2 · Accepted Answer · answered Apr 26 '18 at 15:37

You could create a new object by iterating the keys and use Object.assign with computed property names.

var lastThreeYearsArr = ['currYear', 'currYear-1', 'currYear-2'],
    object = lastThreeYearsArr.reduce((o, k) => Object.assign(o, { [k]: 0 }), {});
    
console.log(object);

score 0 · Answer 2 · answered Apr 26 '18 at 15:40

0

You can specify the properties using bracket notation instead of the object literal notation. For example:

const x = [2011, 2012, 2013]
let y = {}
y[x[0]] = 0

answered Apr 26 '18 at 15:40

DaveG

445
1
3
14

score 0 · Answer 3 · answered Apr 26 '18 at 15:41

use a simple forEach and assign new properties with bracket notation :

const currYear = (new Date()).getFullYear();
const lty = [currYear, currYear - 1, currYear - 2]

let result = {};

lty.forEach((e, i) => {
  result[e] = 0
})

console.log(result)

score 0 · Answer 4 · answered Apr 26 '18 at 15:45

Enclose each key with brackets [] which are used for computed property names

You can use Object.assign as already suggested but if IE compatibility is required a basic loop will do too.

var currYear = 2018;
var lastThreeYearsArr = [currYear, currYear - 1, currYear - 2]

var obj = {};

for (var i = 0; i < lastThreeYearsArr.length; i++) {
    obj[lastThreeYearsArr[i]] = 0;
}

console.log(obj);

Javascript object - using array value as key

4 Answers4