break array of objects into a new array based on property

Question

I have to transform an array and I don't know how to, anyone can help me with this?

I have this array:

[
  {clientid: 1, content: 'abc'},
  {clientid: 2, content: 'abc'},
  {clientid: 3, content: 'abc'},
  {clientid: 3, content: 'abc'},
  {clientid: 2, content: 'abc'},
  {clientid: 1, content: 'bcd'},
  {clientid: 2, content: 'abc'},
  {clientid: 1, content: 'def'},
  {clientid: 3, content: 'abc'}
]

and I need an array like this:

[
  { clientid: 1, content: ['abc', 'bcd', 'def'] },
  { clientid: 2, content: ['abc', 'abc', 'abc'] },
  { clientid: 3, content: ['abc', 'abc', 'abc'] },

]

anyone can help me?

Welcome to Stackoverflow. Please take the tour (and get a badge). Your question lacks any attempt at solving this problem on your own. The idea is for you to try to get something to work and then come here with specific problems you are unable to resolve. Taking the tour and reading about How to ask a good question in the help center will provide all the information you need. — Randy Casburn
– Randy Casburn, Commented Oct 29, 2020 at 17:30
Does this answer your question? Most efficient method to groupby on an array of objects — Anurag Srivastava
– Anurag Srivastava, Commented Oct 29, 2020 at 17:32
I somewhat disagree. it has clearly stated input and required output. why clutter the question with his failed attempts its just noise. and Derek answered with that outstanding answer. I think this is a good addition to the stack overflow question repository — Bryan Dellinger
– Bryan Dellinger, Commented Oct 29, 2020 at 17:39
I agree with @BryanDellinger ... It sounds like the OP hit a wall. The question's sufficient to assist anyway. If I have gripes, I'd say it's with the title. Maybe "How to transform an array of objects to group one attribute by another" or something? — chad_
– chad_, Commented Oct 29, 2020 at 17:41
@BryanDellinger Somewhat agree with you, the problem may be quite difficult for op to post a solution which may not even near to completion. — Abhishek Gurjar
– Abhishek Gurjar, Commented Oct 29, 2020 at 17:41

Derek Wang · Accepted Answer · 2020-10-29 17:31:03Z

4

This can be done using Array.prototype.reduce.

const input = [
  {clientid: 1, content: 'abc'},
  {clientid: 2, content: 'abc'},
  {clientid: 3, content: 'abc'},
  {clientid: 3, content: 'abc'},
  {clientid: 2, content: 'abc'},
  {clientid: 1, content: 'bcd'},
  {clientid: 2, content: 'abc'},
  {clientid: 1, content: 'def'},
  {clientid: 3, content: 'abc'}
];

const groupBy = input.reduce((acc, cur) => {
  acc[cur.clientid] ? acc[cur.clientid].content.push(cur.content) : acc[cur.clientid] = {
    clientid: cur.clientid,
    content: [ cur.content ]
  };
  return acc;
}, {});
const output = Object.values(groupBy);
console.log(output);

answered Oct 29, 2020 at 17:31

Derek Wang

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