Generate array of objects based on object of objects

Question

I have an object like this:

const phrases = {
 1:{
 sentenceID: 1,
 reference: "some phrase",
 },
 2:{
 sentenceID: 2,
 reference: "It was in",
 },
 
 3:{
 sentenceID: 2,
 reference: "Grand Pabbie's visions",
 },
 
 4:{
 sentenceID: 2,
 reference: "visions",
 },
 
 5:{
 sentenceID: 3,
 reference: "another phrase of a sentence",
 },
 
 6:{
 sentenceID: 3,
 reference: "and this is one more phrase",
 },
 
};

And I want to create an array of objects in which each object in the new array is based on same sentenceIDs...

In other words I want the objects in the new array with same sentenceIDs.

So the desired result would be this:

result = [
 {
 1: {
 sentenceID: 1,
 reference: "some phrase",
 },
 },
 {
 2: {
 sentenceID: 2,
 reference: "It was in",
 },
 3: {
 sentenceID: 2,
 reference: "Grand Pabbie's visions",
 },
 4: {
 sentenceID: 2,
 reference: "visions",
 },
 },
 {
 5: {
 sentenceID: 3,
 reference: "another phrase of a sentence",
 },
 6: {
 sentenceID: 3,
 reference: "and this is one more phrase",
 },
 }
]

• Nina Scholz: what goes wrong? please add your code.
• Sara Ree: Nothing ... I just need you again Nina!
• Barmar: What's the logic here? Why is 1 in an object of its own, but 2, 3, 4 are collected in a single object?
• Barmar: Ah, they're grouped by sentenceID
• Barmar: Loop through the original object, creating a new object that uses sentenceID as the key, and the value is the new grouped objects you want to create in the result.

Answer 1

Simply group by sentenceID.

const
 phrases = { 1: { sentenceID: 1, reference: "some phrase" }, 2: { sentenceID: 2, reference: "It was in" }, 3: { sentenceID: 2, reference: "Grand Pabbie's visions" }, 4: { sentenceID: 2, reference: "visions" }, 5: { sentenceID: 3, reference: "another phrase of a sentence" }, 6: { sentenceID: 3, reference: "and this is one more phrase" } },
 result = Object.values(Object.entries(phrases).reduce((r, [k, o]) => {
 r[o.sentenceID] ??= {};
 r[o.sentenceID][k] = o;
 return r;
 }, {}));
console.log(result)

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

• Ben Stephens: If anyone else hasn't seen ??= before: developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/…

Answer 2

You can use .reduce to loop over the entries of phrases and group the items by the sentenceID:

const phrases = {
 1: { sentenceID: 1, reference: "some phrase" },
 2: { sentenceID: 2, reference: "It was in" },
 3: { sentenceID: 2, reference: "Grand Pabbie's visions" },
 4: { sentenceID: 2, reference: "visions" },
 5: { sentenceID: 3, reference: "another phrase of a sentence" },
 6: { sentenceID: 3, reference: "and this is one more phrase" },
};
// iterate over the entries
let res = Object.entries(phrases).reduce((acc,item) => {
 // get the key and value of the current entry
 const [key, value] = item;
 
 // get the attribute we're grouping by 
 const { sentenceID } = value;
 
 // check if acc already has this sentenceID
 const prev = acc[sentenceID];
 if(!prev) acc[sentenceID] = {};
 
 // update the subcategory
 acc[sentenceID][key] = value;
 
 return acc;
}, {});
// get subcategories grouped by sentence ID
res = Object.values(res);
console.log(res);

Answer 3

Using set:

let phrases={1:{sentenceID:1,reference:"some phrase"},2:{sentenceID:2,reference:"It was in"},3:{sentenceID:2,reference:"Grand Pabbie's visions"},4:{sentenceID:2,reference:"visions"},5:{sentenceID:3,reference:"another phrase of a sentence"},6:{sentenceID:3,reference:"and this is one more phrase"}};
let entries = Object.entries(phrases)
let result = [... new Set(entries.map(([k,v]) => v.sentenceID))]
 .map(e => Object.fromEntries(entries.filter( ([k,v]) => v.sentenceID === e )))
 
 
 
console.log(result)