How to use array method to combine objects with same property value in an array

Question

const input = [{diagramId: 123, data: [{id: 1, content: content1}]},
                  {diagramId: 123, data: [{id: 2, content: content2}, 
                                          {id: 23, content: conent23}] },
                  {diagramId: 234, data: [{id: 3, content: content3}]}]

Desired output: 
const output = [{diagramId: 123, data: [{id: 1, content: content1},
                                        {id: 2, content: content2},
                                        {id: 23, content: content23}]}, 
                {diagramId: 234, data: [{id: 3, content: content3}]}]

As you can see above, I want to array method to combine objects that share the same property value (diagramId) to form a new object that condenses their other property together into an array under the other property.

I used for loops, but was rejected for PR due to readability issues. Is it possible to use Array.reduce() to do this?

DecPK · Accepted Answer · 2021-04-14 23:17:46Z

4

Yeah, you can easily achieve this using reduce

const input = [
  { diagramId: 123, data: [{ id: 1, content: "content1" }] },
  {
    diagramId: 123,
    data: [
      { id: 2, content: "content2" },
      { id: 23, content: "conent23" },
    ],
  },
  { diagramId: 234, data: [{ id: 3, content: "content3" }] },
];


const result = input.reduce((acc, curr) => {
  const { diagramId, data } = curr;
  const findObj = acc.find((o) => o.diagramId === diagramId);
  if (!findObj) {
    acc.push({ diagramId, data });
  } else {
    findObj.data.push(...data);
  }
  return acc;
}, []);

console.log(result);

answered Apr 14, 2021 at 23:17

DecPK

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1 Comment

LWang Over a year ago

Thanks for quick reply! I got lost on the return acc part. Thanks.

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