Compare two arrays of objects in underscorejs

Question

I have two arrays of objects

var arr1 =
    [
    {
        "lastInteracted": "2016-03-31T11:13:09.000Z",
        "email": "[email protected]",
        "interactionCount": 2
    },
    {
        "lastInteracted": "2016-03-31T21:06:19.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-29T11:15:41.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    }
    ]

and

var arr2 =
[
    {
        "lastInteracted": "2016-03-31T11:13:09.000Z",
        "email": "[email protected]",
        "interactionCount": 2
    },
    {
        "lastInteracted": "2016-03-31T21:06:19.000Z",
        "email": "[email protected]",
        "interactionCount": 4
    },
    {
        "lastInteracted": "2016-03-29T11:15:41.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 10
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 18
    }
]

I want to merge these two arrays such that if the email of an object exists in both then diff the interactionCount from arr1 with arr2 else return the interactionCount of either arr1 or arr2.

Result will be

var result = [
    {
        "lastInteracted": "2016-03-31T11:13:09.000Z",
        "email": "[email protected]",
        "interactionCount": 0
    },
    {
        "lastInteracted": "2016-03-31T21:06:19.000Z",
        "email": "[email protected]",
        "interactionCount": -4
    },
    {
        "lastInteracted": "2016-03-29T11:15:41.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-29T11:15:41.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 1
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 10
    },
    {
        "lastInteracted": "2016-03-24T10:02:29.000Z",
        "email": "[email protected]",
        "interactionCount": 18
    }
]

Possible duplicate of Merging two collections using Underscore.JS — alexmac
– alexmac, Commented Apr 12, 2016 at 7:56
I have gone through those solutions but they don't do what I need. If you can look the results array, maybe it will be much more clearer as I don't only want to eliminate duplicates but also get a diff of the values wherever the duplicates are present. — Naveen Paul
– Naveen Paul, Commented Apr 12, 2016 at 8:04

Cyril Cherian · Accepted Answer · 2016-04-12 10:39:13Z

1

Using underscore you can do it like this:

var arr1 = [{
  "lastInteracted": "2016-03-31T11:13:09.000Z",
  "email": "[email protected]",
  "interactionCount": 2
}, {
  "lastInteracted": "2016-03-31T21:06:19.000Z",
  "email": "[email protected]",
  "interactionCount": 1
}, {
  "lastInteracted": "2016-03-29T11:15:41.000Z",
  "email": "[email protected]",
  "interactionCount": 1
}, {
  "lastInteracted": "2016-03-24T10:02:29.000Z",
  "email": "[email protected]",
  "interactionCount": 1
}]
var arr2 = [{
  "lastInteracted": "2016-03-31T11:13:09.000Z",
  "email": "[email protected]",
  "interactionCount": 2
}, {
  "lastInteracted": "2016-03-31T21:06:19.000Z",
  "email": "[email protected]",
  "interactionCount": 4
}, {
  "lastInteracted": "2016-03-29T11:15:41.000Z",
  "email": "[email protected]",
  "interactionCount": 1
}, {
  "lastInteracted": "2016-03-24T10:02:29.000Z",
  "email": "[email protected]",
  "interactionCount": 1
}, {
  "lastInteracted": "2016-03-24T10:02:29.000Z",
  "email": "[email protected]",
  "interactionCount": 10
}, {
  "lastInteracted": "2016-03-24T10:02:29.000Z",
  "email": "[email protected]",
  "interactionCount": 18
}]

var ary = _.chain(arr1.concat(arr2))//use chain
  .groupBy(function(d) {
    return d.email;
  })//grouping by email
  .map(function(d) {
    var last = _.last(d);//take the last in the group
    var k = {
      email: last.email,
      lastInteracted: last.lastInteracted,
      interactionCount: _.reduce(d, function(memo, d1) {
        return memo + d1.interactionCount;//sum up interactionCount
      }, 0)
    };
    return k;
  }).value()

document.write('<pre>' + JSON.stringify(ary, 0, 4) + '</pre>');

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore.js"></script>

working fiddle here

edited Apr 12, 2016 at 10:39

answered Apr 12, 2016 at 10:27

Cyril Cherian

32.4k7 gold badges48 silver badges57 bronze badges

Sign up to request clarification or add additional context in comments.

5 Comments

Naveen Paul Over a year ago

The Jsfiddle doesn't work. It just prints some functions from the library.

Naveen Paul Over a year ago

Thanks for the quick update. If try to subtract interactionCounts, Why does it just append '-' to the sum of interactionCounts?

Cyril Cherian Over a year ago

I think the question is about adding interactionCounts why are you subtracting?

Naveen Paul Over a year ago

My bad I completely missed writing the the expected results. I should actually be getting a diff of the two array's interactionCount. I need to track if the interactionCount have increased or decreased over those two arrays.

Naveen Paul Over a year ago

Thank you so much @cyril! I really can't believe you actually helped me after I basically changed the requirement. Thanks again :-) :-)

Collectives™ on Stack Overflow

Compare two arrays of objects in underscorejs

1 Answer 1

5 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

5 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related