JS Object Update + React Reducer

Question

I'm struggling to update all "new" attributes to false. Below is an example object:

const msgdata = {
"1511207758": {
    "userid": "1000015977",
    "text": "hello",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2017-11-20T19:55:58.000Z"
},
"1511277428": {
    "userid": "1000000000",
    "text": "hey hi",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2017-11-21T15:17:08.000Z"
},
"1640341426": {
    "userid": "1000000000",
    "text": "hellow how are you?",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:23:45.706Z"
},
"1640342296": {
    "userid": "1000000000",
    "text": "asdfasdf",
    "new": true,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:38:16.089Z"
},
"1640342382": {
    "userid": "1000000000",
    "text": "fxvfv",
    "new": true,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:39:41.910Z"
}
}

when I try the following I mess up the object structure changes to an array but I need to maintain the object/key structure - just change the new value to false.

    let newMessages = {}
    if (payload.length > 0) {
        payload.map((item) => {
            if (messagesData && messagesData[item.userid]) {
                newMessages = Object.keys(messagesData[item.userid].messages).map((key) => ({ ...newMessages[item.userid].messages[key], new: false }))
            }
            return true
        })

        console.dir('newMessages')
        console.dir(newMessages)

The return object is a standard array - map does that... eg: 0,1,2 keys...

How can I maintain the object structure and just change the new attr?

Use Object.entries(msgdata).reduce((acc, [key, value]) => { ... }, {}); and inside the function, do acc[key] = { ...value, new: false }; to set the copy's keys, then return acc; (not posting this as answer obviously and deliberately, for anybody who's wondering) — user5734311
– user5734311, Commented Dec 24, 2021 at 23:42

axtck · Accepted Answer · 2021-12-24 23:52:50Z

You could map() the objects entries, change the new value to false and return entries to create a new object from.

const msgdata = {
  "1511207758": {
    "userid": "1000015977",
    "text": "hello",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2017-11-20T19:55:58.000Z"
  },
  "1511277428": {
    "userid": "1000000000",
    "text": "hey hi",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2017-11-21T15:17:08.000Z"
  },
  "1640341426": {
    "userid": "1000000000",
    "text": "hellow how are you?",
    "new": false,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:23:45.706Z"
  },
  "1640342296": {
    "userid": "1000000000",
    "text": "asdfasdf",
    "new": true,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:38:16.089Z"
  },
  "1640342382": {
    "userid": "1000000000",
    "text": "fxvfv",
    "new": true,
    "subjecttitle": null,
    "subjectcontent": null,
    "datetime": "2021-12-24T10:39:41.910Z"
  }
}

const result = Object.fromEntries(Object.entries(msgdata).map(([k, v]) => {
  return [k, { ...v, new: false }]
}));

console.log(result);

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