NodeJS Restructure Array of Objects

Question

I've got the following data - array of objects Its a sender ID and a message

[
    {
        "sender": "1000000000",
        "message": message 1"
    }, 
    {
        "sender": "1000000000",
        "message": "message 2"
    },
    {
        "sender": "1000000001",
        "message": "message 3"
    }, 
    {
        "sender": "1000000002",
        "message": "message 4"
    },
    {
        "sender": "1000000002",
        "message": "message 5"
    }, 
    {
        "sender": "1000000002",
        "message": "message 6"
    }
]

I want to create a new array of objects that is structured like below. So the messages are grouped by the sender. It will help with displaying the data.

[
    {
        "sender": "1000000000",
        "messages": [
              "message 1",
              "message 2",
         ]
    },
    {
        "sender": "1000000001",
        "messages": [
              "messages 3"
        ]
    }, 
    {
        "sender": "1000000002",
        "messages": [
              "message 4",
              "message 5",
              "message 6"
        ]
    }
]

I've been playing with .map() and .filter() - but I'm a long way off.

I've also tried for loops etc which I might be able to get working but they are ugly.

Is there an easy what to change the structure?

thankyou!

17,3k rep and yet... What have you tried so far to solve this on your own? Add the most promising approach, explain the problems you have with that, preferable with a snippet -> [How do I ask a good question?](https://stackoverflow.com/help/how-to-ask) — Andreas, Aug 18 '21 at 11:19
There are a bunch of questions on how to group an array of objects: [How much research effort is expected of Stack Overflow users?](https://meta.stackoverflow.com/questions/261592/how-much-research-effort-is-expected-of-stack-overflow-users) — Andreas, Aug 18 '21 at 11:20

score 2 · Accepted Answer · answered Aug 18 '21 at 11:24

You can use Array.reduce() to group your messages by sender:

const data = [ { "sender": "1000000000", "message": "message 1" }, { "sender": "1000000000", "message": "message 2" }, { "sender": "1000000001", "message": "message 3" }, { "sender": "1000000002", "message": "message 4" }, { "sender": "1000000002", "message": "message 5" }, { "sender": "1000000002", "message": "message 6" } ] 
const result = Object.values(data.reduce((acc, cur) => { 
    acc[cur.sender] = acc[cur.sender] || { sender: cur.sender, messages: []};
    acc[cur.sender].messages.push(cur.message);
    return acc;
}, {}));

console.log("Result:", result);

Please don't add yet another _"group by"_ answer. There are already hundreds of similar questions and really good answers for this topic... — Andreas, Aug 18 '21 at 11:27

NodeJS Restructure Array of Objects

1 Answers1