How can I filter an array to remove duplicate entries?

Question

I have an array of data returned from my server. From this array I need to get an array of Topics and an array of SubTopics:

var data = 
[
{"topicId":1,"subTopicId":1,"topicName":"J","subTopicName":" Ar"},
{"topicId":1,"subTopicId":2,"topicName":"J","subTopicName":" Us"},
{"topicId":1,"subTopicId":3,"topicName":"J","subTopicName":" Ut"},
{"topicId":2,"subTopicId":4,"topicName":"L","subTopicName":" Ov"},
{"topicId":2,"subTopicId":5,"topicName":"L","subTopicName":" El"},
{"topicId":2,"subTopicId":6,"topicName":"L","subTopicName":" In"},
{"topicId":2,"subTopicId":7,"topicName":"L","subTopicName":" Pr"},
{"topicId":2,"subTopicId":8,"topicName":"L","subTopicName":" Va"},
{"topicId":2,"subTopicId":9,"topicName":"L","subTopicName":" Pa"}
]

I have code that I use to reformat this data and just give me topic information:

var topics = data.map(function (t) {
                    return {
                        id: t.topicId, name: t.topicName
                    };
                });

But this gives me three entries for topicId 1 and six entries for topidId 2.

How I can filter out duplicate entries so I can for example the above would just give me a topic array of two entries. One for each topicId

Please no jQuery, lodash or other framework solutions as I didn't include these in the tags. thanks

knpsck · Accepted Answer · 2014-11-05 11:16:14Z

1

This should work

topics = data.filter(function(item, index, data) {
   for (var i = 0; i < data.length; i++) {
      if (item.topicId === data[i].topicId) break;
   }

   return index === i;
}).map(function (item) {
    return {
        id: item.topicId,
        name: item.topicName
    };
});

If duplicate entries are equal, you can simplify filter function

data.filter(function(item, index, data) {   
   return data.indexOf(item) === index;
})

answered Nov 5, 2014 at 11:16

knpsck

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Comments

CuriousSuperhero · Accepted Answer · 2014-11-05 11:11:59Z

Here is the solution:

var data = 
[
{"topicId":1,"subTopicId":1,"topicName":"J","subTopicName":" Ar"},
{"topicId":1,"subTopicId":2,"topicName":"J","subTopicName":" Us"},
{"topicId":1,"subTopicId":3,"topicName":"J","subTopicName":" Ut"},
{"topicId":2,"subTopicId":4,"topicName":"L","subTopicName":" Ov"},
{"topicId":2,"subTopicId":5,"topicName":"L","subTopicName":" El"},
{"topicId":2,"subTopicId":6,"topicName":"L","subTopicName":" In"},
{"topicId":2,"subTopicId":7,"topicName":"L","subTopicName":" Pr"},
{"topicId":2,"subTopicId":8,"topicName":"L","subTopicName":" Va"},
{"topicId":2,"subTopicId":9,"topicName":"L","subTopicName":" Pa"}
]

var arr = [],
    collection = [];

$.each(data, function (index, value) {
    if ($.inArray(value.topicId, arr) == -1) {
        arr.push(value.topicId);
        collection.push(value);
    }
});
console.log(collection);

This will print the following into console:

enter image description here

Gilsha · Accepted Answer · 2014-11-05 11:12:17Z

0

Try this

var topicIds = {};
var unique = [];
topics.forEach(function(t){ 
      if(!topicIds[t.id]){ 
          unique.push(t); 
          topicIds[t.id] = true; 
      } 
});

unique will have unique array of topics.

answered Nov 5, 2014 at 11:12

Gilsha

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Comments

Varon · Accepted Answer · 2014-11-05 11:12:28Z

0

I suggest to use the smart library underscore.js http://underscorejs.org/

They implement functional behaviors like groupBy http://underscorejs.org/#groupBy

So you can simply use _.groupBy(data, function(t){return t.topicId;}) and you get grouped suptopics:

Object {1: Array[3], 2: Array[6]}
1: Array[3]
    [{
        subTopicId: 1
        subTopicName: " Ar"
        topicId: 1
        topicName: "J"
    },{
        subTopicId: 2
        subTopicName: " Us"
        topicId: 1
        topicName: "J"
    }, ... ]

answered Nov 5, 2014 at 11:12

Varon

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