Sort an object by key names specified in an array

Question

I have an object with simple key value pairs and an array with just key names. I would like to sort the objects keys by the order of the keys in the array.

A simplified example:

const obj = {
"bread": 11,
"butter": 6,
"milk": 40,
}

const orderedKeys = ["milk", "butter", "bread"]

const expectedResult = {
"milk": 40,
"butter": 6,
"bread": 11,
}

In this example I know the amount of keys in both the array and the object, however in reality I don't know the amount and in reality the object can also have more keys than specified in the array. In this case I just want the unknown keys at the end of the object.

What would be the cleanest way to solve this problem?

Yves Kipondo · Accepted Answer · 2020-09-18 13:58:03Z

2

You can take advantage of Array.prototype.reduce which allow to perform different manipulation on array and return another kind of object or array

const obj = {
"bread": 11,
"butter": 6,
"milk": 40,
}

const orderedKeys = ["milk", "butter", "bread"]

const expectedResult = orderedKeys.reduce((accumulator, current) => {
   return {...accumulator, [current]: obj[current]};

}, {})

console.log(expectedResult);

If you want to add key which aren't present in the orderedKey but are present inside of the obj you can perform it like this

const obj = {
    "bread": 11,
    "butter": 6,
    "milk": 40,
    "cheese": 5
}

const orderedKeys = ["milk", "butter", "bread"]

let expectedResult = orderedKeys.reduce((accumulator, current) => {
    return {...accumulator, [current]: obj[current]};
}, {});

expectedResult = Object.assign({}, expectedResult, obj);
console.log(expectedResult);

edited Sep 18, 2020 at 13:58

answered Sep 18, 2020 at 13:43

Yves Kipondo

5,6931 gold badge22 silver badges33 bronze badges

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

Comments

Lionel Rowe · Accepted Answer · 2020-09-18 14:02:43Z

The simplest way is probably this:

map the ordered keys to [key, value] tuples
Reconstruct the object from those using Object.fromEntries
...spread the remaining object properties

const obj = {
    unknown: 15,
    bread: 11,
    butter: 6,
    milk: 40,
}

const orderedKeys = ['milk', 'butter', 'bread']

const orderedObj = {
    ...Object.fromEntries(orderedKeys.map(k => [k, obj[k]])),
    ...obj,
}

console.log(orderedObj)

However, relying on the order of keys in an object is generally a bad idea, because JavaScript objects are typically considered to be unordered ({ a: 1, b: 2 } is usually considered equivalent to { b: 2, a: 1 }). Whether or not they're ordered in practice depends somewhat on implementation. For this reason, and depending on your use case, you could consider using a Map instead:

new Map(orderedObj)

Collectives™ on Stack Overflow

Sort an object by key names specified in an array

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related