How to remove duplicate names from array of objects

Question

var arr = [
    {level:0,name:"greg"},
    {level:0,name:"Math"},
    {level:0,name:"greg"}
];

I have tried the following:

function removeDuplicates:(dataObject){
    self.dataObjectArr = Object.keys(dataObject).map(function(key){
        return dataObject[key];
    });

    for(var i= 0; i < self.dataObjectArr.length; i++ ){
        self.dataObjectArr[i]['name'] = self.dataObjectArr[i];

        self.uniqArr = new Array();
        for(var key in self.dataObjectArr){
            self.uniqArr.push(self.dataObjectArr[key]);
        }
    }
    self.uniqObject = DataMixin.toObject(self.uniqArr);
    return self.uniqObject;
}

But I get error saying: Uncaught TypeError: Converting circular structure to JSON.

Seems your function declaration has an `:` here -> `function removeDuplicates:(dataObject)` ? — David R, Sep 28 '16 at 07:10
You can use `underscore` check this answer http://stackoverflow.com/questions/9923890/removing-duplicate-objects-with-underscore-for-javascript — Davide, Sep 28 '16 at 07:14

score 2 · Answer 1 · edited May 23 '17 at 12:19

Here's a generic "uniquify" function:

function uniqBy(a, key) {
    var seen = new Set();
    return a.filter(item => {
        var k = key(item);
        return !seen.has(k) && seen.add(k)
    });
}

///

var arr = [
    {level:0,name:"greg"},
    {level:0,name:"greg"},
    {level:0,name:"joe"},
    {level:0,name:Math},
    {level:0,name:"greg"},
    {level:0,name:"greg"},
    {level:0,name:Math},
    {level:0,name:"greg"}
];

uniq = uniqBy(arr, x => x.name);
console.log(uniq);

See here for the in-depth discussion.

score 2 · Accepted Answer · answered Sep 28 '16 at 07:20

2

You should push the name to an array or a set and check the same in the following..

var arr = [{
  level: 0,
  name: "greg"
}, {
  level: 0,
  name: "Math"
}, {
  level: 0,
  name: "greg"
}]

function removeDuplicates(arr) {
  var temp = []
  return arr.filter(function(el) {
    if (temp.indexOf(el.name) < 0) {
      temp.push(el.name)
      return true
    }
  })
}

console.log(removeDuplicates(arr))

answered Sep 28 '16 at 07:20

Pranesh Ravi

18,642
9
46
70

What is `temp.indexOf(el.name) < 0` doing? – kittu Oct 07 '16 at 09:10
less than 0 mean -1(not found)?? Could you please explain – kittu Oct 07 '16 at 09:11
Exactly, if not found, `indexOf()` will return -1 – Pranesh Ravi Oct 07 '16 at 09:12
I know that but how is it removing duplicates with this logic I am not able to understand – kittu Oct 07 '16 at 09:22
Initially I'm checking if the name exist in `temp[]`, if not preset, I'll push that to `temp` and return `true` to `filter()` which will return the object to the array. Next time if I find the same name I return false to filter which will ignore that object. So the duplicates will be removed – Pranesh Ravi Oct 07 '16 at 09:25
where are we returning false? – kittu Oct 07 '16 at 09:28
1

I'm not returning `false` explicitly. If nothing is returned, it'll be taken as `undefined`, which is the same like `false` – Pranesh Ravi Oct 07 '16 at 09:31

score 0 · Answer 3 · answered Sep 28 '16 at 07:24

I believe you have a syntax error " removeDuplicates:(dataObject){ ..."

should be without the ":" >> " removeDuplicates(dataObject){ ... " "

You can try this :

function removeDuplicates(arr){
    var match={}, newArr=[];
    for(var i in arr){ if(!match[arr[i].name]){ match[arr[i].name]=1; var newArr=i; } }
    return newArr;
}

arr = removeDuplicates(arr);

guest271314 · Answer 4 · 2016-09-28T07:46:54.193

0

You can use $.unique(), $.map(), $.grep()

var arr = [
  {level:0,name:"greg"},
  {level:0,name:"Math"},
  {level:0,name:"greg"}
];

var res = $.map($.unique($.map(arr, el => el.name)), name => 
            $.grep(arr, el => el.name === name)[0]);

jsfiddle https://jsfiddle.net/4tex8xhy/3

edited Sep 28 '16 at 07:46

answered Sep 28 '16 at 07:30

guest271314

1
15
104
177

score 0 · Answer 5 · answered Sep 28 '16 at 07:48

Or you can use such libraries as underscore or lodash (https://lodash.com/docs/4.16.2). Lodash example:

var arr = [
    {level:0,name:"greg"},
    {level:0,name:"Math"},
    {level:0,name:"greg"}
];

var result = _.map(_.keyBy(arr,'name'));

//result will contain
//[
//   {
//    "level": 0,
//    "name": "greg"
//    },
//    {
//    "level": 0,
//    "name": "Math"
//    }
//]

Ofc. one thing to always consider in these tasks, what do you want exactly are you going to do: modify an existing array, or get a new one back. This example returns you a new array.

How to remove duplicate names from array of objects

5 Answers5