Find duplicates in nested object

Question

Assuming that I have a JS object wich contains other objects inside it, but all of them have the same structure. I am trying to search inside them for any duplicated values. For example:

{
    {
        id: "123"
        name: "John"
        surname: "Smith"
        phone: "123456789"
    }, 
    {
        id: "456"
        name: "Jack"
        surname: "Jones"
        phone: "9876789123"
    }, 
    {
        id: "789"
        name: "John"
        surname: "Doe"
        phone: "123456789"
    }
}

I want to search and find that the property 'phone' with value '123456789' is the same on both objects with ids '123' and '789'.

Note: the property/value combination that I am searching for is unknown beforehand.

ahem... altogether now: what have you tried?

Dancrumb
– Dancrumb

2013-05-16 16:48:38 +00:00
Commented May 16, 2013 at 16:48 — Dancrumb
– Dancrumb, Commented May 16, 2013 at 16:48

score 2 · Accepted Answer · 2013-05-16 17:14:59Z

2

First, if the outer structure is a plain Object, use an Array instead. If you can't change the structure, I'd convert it first.

DEMO: http://jsfiddle.net/3Y2qr/

if (!Array.isArray(data))
    data = Object.keys(data)
                 .sort(function(a,b) { return a - b })
                 .map(function(key) { return data[key] })

Then you can reduce the set to groups of matches.

var groupByPhone = data.reduce(function(found, obj) {
    if (found[obj.phone])
        found[obj.phone].push(obj)
    else
        found[obj.phone] = [obj]
    return found
}, {});

var dupes = Object.keys(groupByPhone)
                  .filter(function(key) {
                      return groupByPhone[key].length > 1
                  })

So now groupByPhone is an object where the keys are the unique phone numbers, and the values are the objects that have that number.

The dupes will be a list of phone number keys that can be used to lookup groups of duplicate objects in groupByPhone.

edited May 16, 2013 at 17:14

answered May 16, 2013 at 17:03

user1106925

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1 Comment

Vassilis Barzokas Over a year ago

Thank you very much, it is exactly what i was looking for. My main problem was that, as you figured out, the outer structure is an Object and i was manipulating it as an Array.

jAndy · Accepted Answer · 2013-05-16 16:50:05Z

0

Array.prototype.filter to the rescue !

var searchFor = '123456789';

var filteredResult = arrayOfObjects.filter(function( obj ) {
    return obj.phone === searchFor;
});

console.log( filteredResult );

answered May 16, 2013 at 16:50

jAndy

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7 Comments

dandavis Over a year ago

you can make it faster by avoiding a closure using this: return obj.phone==this;}, searchFor );

Ian Over a year ago

@dandavis It could also be a lot faster if a normal for loop is used

user1106925 Over a year ago

I think the idea is that the match string isn't known, and OP wants to find duplicates based on the .phone property. Also, I'm not certain that OP has an actual Array, though if not, one should be used.

dandavis Over a year ago

@ian yes, usually for loops are still faster, though not as much faster as they were two years ago. Filter() provides code re-usability that for loops cannot touch, and that often out-weighs raw benchmark performance.

Vassilis Barzokas Over a year ago

@squint you are right, the match string is unknown. I have tried with another combination of filter and i got an error that the object has no method filter

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