removing duplicates from JS array

Question

I have the following JS array:

var items=[
    { id: 1, name: 'aa' },
    { id: 1, name: 'bb' },
    { id: 2, name: 'cc' },
    { id: 1, name: 'dd' }
];

I wan to convert it to the following.

var items=[
    { id: 1, name: 'dd' },
    { id: 2, name: 'cc' }
];

How should I go about it using JavaScript?

http://stackoverflow.com/questions/23507853/remove-duplicate-objects-from-json-array — Vincent Beltman, Sep 30 '14 at 10:24

score 1 · Accepted Answer · answered Sep 30 '14 at 10:27

1

We could actually do this quite simply, just looping over it. For each item, assign its place in the new array corresponding to its ID. Earlier IDs get overwritten, so only the last one is saved.

var items=[
    { id: 1, name: 'aa' },
    { id: 1, name: 'bb' },
    { id: 2, name: 'cc' },
    { id: 1, name: 'dd' }
], newItems = [];
for (var i =0;i<items.length;i++){
    newItems[items[i].id - 1] = items[i];
}
alert(JSON.stringify(newItems));

answered Sep 30 '14 at 10:27

Scimonster

32,893
9
77
89

What if ID was not contiguous? – Adam Sep 30 '14 at 10:29
@Adam Then there'll be a few empty list items. Those can easily be filtered out. – Scimonster Sep 30 '14 at 10:30
@Scimonster - it's a great solutions but, if you want to filtered out data on the bases of any string data than it'll not work. – prog1011 Sep 30 '14 at 11:00
@user3577774 in that case, you can use an object. – Scimonster Sep 30 '14 at 11:10

score 0 · Answer 2 · answered Sep 30 '14 at 10:41

0

Try this:

items = items.reverse().filter((function() {
    var existing = {};
    return function(item) {
        if(existing[item.id]) {
            return false;
        }
        existing[item.id] = true;
        return item;
    }
}()));

answered Sep 30 '14 at 10:41

friedi

4,350
1
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Since we are filtering, yes, let's use `filter`!! The inside could be cleaned up a little bit, however. How about `return !existing[item.id] && existing[item.id] = true;`? – Sep 30 '14 at 11:27

score 0 · Answer 3 · answered Sep 30 '14 at 10:47

This should do what you want:

var items = [
    { id: 1, name: 'aa' },
    { id: 1, name: 'bb' },
    { id: 2, name: 'cc' },
    { id: 1, name: 'dd' }
];

function removeDupIds(items){
    var result  = [],
        uniqIds = {},
        i       = 0,
        l       = items.length;

    for(; i<l; i++){
        uniqIds[items[i].id] = items[i].name;
    }

    for(var k in uniqIds){
        result.push({id: k, name: uniqIds[k]});
    }
    return result;
}

console.log(removeDupIds(items));

score 0 · Answer 4 · answered Sep 30 '14 at 11:13

Using underscore, it would just be

_.uniq(items.reverse(), function(i1, i2) { return i1.id === i2.id; }))

Normally _.uniq removes identical items, but we can pass it the second parameter specifying a function to use to determine if two items are going to be considered identical.

The items.reverse() is needed because the OP seems to want the final item to take priority.

removing duplicates from JS array

4 Answers4