JavaScript reorder object properties given an array of properties

Question

I have a javascript object like:

{
  a: 3,
  b: 10,
  c: 2,
  d: 7,
}

I have an array containing string representations of the property names:

[ "c", "b", "a", "d" ]

How do I rearrange my object so that the properties are arranged in the same order as in the array, eg:

{
  c: 2,
  b: 10,
  a: 3,
  d: 7,
}

The order of properties in an Object is arbitrary. What is the actual goal here? — Chris G, Aug 01 '19 at 13:49
You have to construct a new object and add the properties in the order you want. However I would strongly suggest you re-think the coding strategy that relies on object property ordering, because it will make your code extremely fragile. — Pointy, Aug 01 '19 at 13:49
This really seems like an [XY Problem](http://xyproblem.info/). What is your actual use case? — charlietfl, Aug 01 '19 at 13:53
@ChrisG—not entirely, see [*Does ES6 introduce a well-defined order of enumeration for object properties?*](https://stackoverflow.com/questions/30076219/does-es6-introduce-a-well-defined-order-of-enumeration-for-object-properties) — RobG, Aug 01 '19 at 14:14

score 1 · Accepted Answer · answered Aug 01 '19 at 13:54

Although ECMAScript-6 improved the feature, object properties are still notoriously unordered. A way to fix this would be to use a Map which remembers the original key insertion order.

    const obj = { a: 3, b: 10, c: 2, d: 7 };
const arr = ["c", "b", "a", "d"];

const res = new Map(arr.map(e => [e, obj[e]]));

for (let [key, value] of [...res]) {
  console.log(key, value);
}

_{(The for...of loop is just to show the actual Map, as they aren't shown on the Stack Snippets console.)}

JavaScript reorder object properties given an array of properties

1 Answers1