Removing the duplicates from an array of objects

Question

Duplicate values are being storing into an array of object

Based on the given userID need to out the duplicate userId, if it exist do nothing, else push that userIdinto the teamSocketsList array

But with the below piece of code duplicate values are being stored into an array teamSocketsList

var  TeamUser = {
    userId : userID,
    socketId : socket.id
}

var i = $.inArray( userID, teamSocketsList ); 
if(i == -1){
    teamSocketsList.push(TeamUser);
}else{
        teamSocketsList = jQuery.grep(teamSocketsList, function(value) {
        return value != userID;
    });
}

Actual Result:

[
    {"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"},
    {"userId":1,"socketId":"ZIbgYMLOda_R5QqvAAAN"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"}
]

Expected Result:

[
    {"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"},
]

Edit:

Here I'm expecting userID to be pushed in to an array teamSocketsList based on the condition, if at all the given userID matches in the present list should return false or do nothing. Otherwise, (iff, it's not at all included then) store it into an array with the auto-generated socketId value

The logic which I had tried to implement was to check whether if that array is empty or not and then, traverse all the elements in the array list so that whenever userID were given as an input it must check the condition and then push that element.

Based on the present answers put up, it'll store the duplicate values and then sort it on and assign it back to teamSocketsList, that's fine.

`{"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"}` is different from `{"userId":1,"socketId":"ZIbgYMLOda_R5QqvAAAN"}`. What is the criteria for keeping the first instead of the next one? — briosheje, May 30 '19 at 11:54
For particular `userId` only one unique `socketId` should be assigned @briosheje — Nɪsʜᴀɴᴛʜ ॐ, May 30 '19 at 11:59
@Nishanthॐ I got that, but **how** do you know that the socket id is the first one? it may get inconsistent. — briosheje, May 30 '19 at 12:00
Based on logging on to the team page only one unique `socketId` will be assigned for each user @briosheje — Nɪsʜᴀɴᴛʜ ॐ, May 30 '19 at 12:02
No each time when user logs or refreshes the page generates unique ID that should be stored into an array so as to confirm that user is alive. For more info refer to socket.js. As I'm trying to get the output value for userid logged on @briosheje — Nɪsʜᴀɴᴛʜ ॐ, May 30 '19 at 12:06
`array.filter(function (obj) { return !this[obj.userId] && (this[obj.userId] = true); }, {})` — 3limin4t0r, May 30 '19 at 12:31
Note that `inArray` won't match a numeric value, held in a variable called `userId`, with an object with a property named `userId` holding the same value. — traktor, May 31 '19 at 11:24
How should need to match the element of `userId` with `userID` traversing whole elements in an array. If you could answer edit my question mentioning your name with an answer, so that other readers would benefit a lot. Should we need to use ECMAScript and thank you for reopening @traktor53 — Nɪsʜᴀɴᴛʜ ॐ, May 31 '19 at 12:32

score 0 · Answer 1 · answered May 30 '19 at 12:15

Along with already mentioned values/reduce, you can take advantage of Set():

const myArray = [
    {"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"},
    {"userId":1,"socketId":"ZIbgYMLOda_R5QqvAAAN"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"}
]

const unique = (arr, key) => {
   const keys = new Set();
   return arr.filter(el => !keys.has(el[key]) && keys.add(el[key]));
 };

console.log(unique(myArray, "userId"));

In opposition to other response I can point out that with this method is easier to change array and key without adding code.

score -1 · Answer 2 · answered May 30 '19 at 11:57

use reduce along with Object.values. create an object whose keys are userId. If the key does not exist, create the key and then use Object.values to get the required ouput.

const input = [
    {"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"},
    {"userId":1,"socketId":"ZIbgYMLOda_R5QqvAAAN"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"},
    {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"}
];

const output = Object.values(input.reduce((accu, {userId, socketId}) => {
    if(!accu[userId]) accu[userId] = {userId, socketId};
    return accu;
}, {}));

console.log(output);

score -1 · Answer 3 · answered May 30 '19 at 12:19

How about this function where you pass in your array and the key to get your result

        const convertArrayToObjecByID = ({ array, key }) =>
          array.reduce((obj, item) => {
                return { ...obj, [item[key]]: item };
              }, {})

        const input = [
            {"userId":1,"socketId":"M8xzpi3O0cMHXe-dAAAK"},
            {"userId":1,"socketId":"ZIbgYMLOda_R5QqvAAAN"},
            {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"},
            {"userId":9,"socketId":"XAf1cepsLv-KDpn3AAAQ"}
        ]
        const myObject = convertArrayToObjecByID({ array:input, key:'userId' })
console.log({myObject})
//then if you want it as an array 
    console.log(Object.keys(myObject).map(item => myObject[item]))

score -1 · Answer 4 · answered May 30 '19 at 12:22

-1

You can store your data in the object (key-value pair) and avoid adding duplicate data. For example:

var teamSocketsList = {};

var TeamUser = {
    userId : userID,
    socketId : socket.id
}

teamSocketsList[TeamUser.userId] = TeamUser;

Then if you are adding new user to teamSocketsList, you can easily (without iterating through all elements in the array) check if there are teamUser with that id.

if(teamSocketsList[TeamUser.userId]) // team user exists in the list

answered May 30 '19 at 12:22

Mitro

268
2
8

Although it does not try to answer to OP question I have to point out that this is exactly the way I would implement it to solve the issue before it's generated – Mosè Raguzzini May 30 '19 at 12:44
That would be resulting in storing inconsistent data structure with Team Socket List: [null,{"userId":1,"socketId":"cIoxHto6yK7vw_WeAAAM"},null,null,null,null,null,null,null,{"userId":9,"socketId":"FBVi7peHCrL6r4YcAAAO"}] @MosèRaguzzini – Nɪsʜᴀɴᴛʜ ॐ May 30 '19 at 12:45
when retrieving socket list it wil suffice to apply a simple filter: [].filter(o => o) to get rid of null values. – Mosè Raguzzini May 30 '19 at 12:54
I'm surprised that after getting rid of null values still stores the duplicate data `Team Socket List: [{"userId":9,"socketId":"iYdg8Hpq__dV-tyFAAAJ"},{"userId":1,"socketId":"gQQ247cGqcnFOaX7AAAN"},{"userId":9,"socketId":"vYD0A5UzTCwfFHtgAAAL"},{"userId":9,"socketId":"vYD0A5UzTCwfFHtgAAAL"}]` @MosèRaguzzini – Nɪsʜᴀɴᴛʜ ॐ May 30 '19 at 13:08
@Nishanthॐ it means that the array already held those values. – Mosè Raguzzini May 30 '19 at 13:10

Removing the duplicates from an array of objects

4 Answers4