Change some object keys on an array and maintain order

Question

I am trying to rename some of the properties on a series of objects in an array in order, but I only want to change the name to some of the properties and not having to rebuild the whole object to maintain the same order.

const data = [
  {
    prop1: 'Change key but keep position',
    second: 'Keep same key name and position',
    prop3: 'Change key but keep position',
    fourth: 'Keep same key name and position',
  }
]

const res = data.map(({prop1, prop3, ...obj}) => ({
  first: prop1,
  third: prop3,
  ...obj,
}))


console.log(res)

.as-console-wrapper { max-height: 100% !important; top: 0; }

Desired output

[
 {
   first: 'Change key but keep position',
   second: 'Keep same key name and position',
   third: 'Change key but keep position',
   fourth: 'Keep same key name and position'
 }
]

I need it to be `first, second, third and fourth` but I don't know how, without rebuildiung the entire object — Álvaro, Aug 15 '21 at 15:17
The order of object keys are not guaranteed. Therefore relying on them seems bad practice. This thread might help: https://stackoverflow.com/questions/5525795/does-javascript-guarantee-object-property-order — Harun Yilmaz, Aug 15 '21 at 15:18
Does this answer your question? [JS rename an object key, while preserving its position in the object](https://stackoverflow.com/questions/48082071/js-rename-an-object-key-while-preserving-its-position-in-the-object) — Heretic Monkey, Aug 15 '21 at 15:22
The only reason to care about the property order is if you are iterating these objects with `for (x in obj)` (or `for..of`). Most modern use of objects to display data either involves a template, where each object property is inserted into the right place, and the template is how order is maintained, or an array of keys, like `['first', 'second', 'fourth', 'third'].map(x => obj[x])` — James, Aug 15 '21 at 15:54
That's all well and good, but can you order this array of objects without having to rebuild the entire object? — Álvaro, Aug 15 '21 at 15:57

score 2 · Accepted Answer · answered Aug 15 '21 at 16:02

Maybe something like this:

const data = [
  {
    prop1: 'Change key but keep position',
    second: 'Keep same key name and position',
    prop3: 'Change key but keep position',
    fourth: 'Keep same key name and position',
  }
];

const renameMap = { prop1: 'first', prop3: 'third'};

const res = data.map(
  obj => Object.fromEntries(Object.entries(obj).map(
    ([key, value]) => [renameMap[key] ?? key, value]
  ))
);

console.log(res);

Thanks, that's exactly what I needed – Álvaro Aug 15 '21 at 16:05 — Álvaro, Aug 15 '21 at 16:05

Change some object keys on an array and maintain order

1 Answers1