Nested duplicate arrays in objects

Question

I am trying to take an array of objects and do 2 things.

1.) Remove objects from the array that are duplicated, create a new array with the names of the items that were duplicates.

Original:

var duplicates = [];

var objects = [
    {
        name: 'foo',
        nums: [1,2]
    },
    {
        name: 'bar',
        nums: [3,2]
    },
    {
        name: 'baz',
        nums: [1,2]
    },
    {
        name: 'bum',
        nums: [2,3]
    },
    {
        name: 'bam',
        nums: [1,2]
    },
]

Desired Output:

duplicates = ['foo', 'baz', 'bam'];

objects = [
    {
        name: 'bar',
        nums: [3,2]
    },
    {
        name: 'bum',
        nums: [2,3]
    }
]

Can anyone help with this? I am using lodash in my project.

What if you have duplicates of both [1,2] and [3,4]? They all go into duplicates? — Barmar
– Barmar, Commented Jan 9, 2015 at 1:22
When you say 'duplicate', do you mean the arrays are the same object, or that the arrays have the same length and order of items, or have the same length but not order of items? — Xotic750
– Xotic750, Commented Jan 9, 2015 at 1:24
Isn't this the same question? stackoverflow.com/questions/27852356/… — Xotic750
– Xotic750, Commented Jan 9, 2015 at 1:24
@Barmar In my particular problem, there will never be multiple duplicates. I am dealing with a array of 3 sub arrays and while it's possible that all 3 match, in most cases, only 2 of them will match — Scotty Bollinger
– Scotty Bollinger, Commented Jan 9, 2015 at 16:43
@Xotic750 It's similar but it's actually the entire solution, and the other was a component of a certain way I was trying to solve my problem. Thought it beneficial to leave both. To answer your question, the order will always be the same so there would never be a [1,2] and a [2,1] and if so I would not want them to be counted as duplicates. — Scotty Bollinger
– Scotty Bollinger, Commented Jan 9, 2015 at 16:44

nullpotent · Accepted Answer · 2015-01-09 21:39:16Z

1

If order of elements in nums array matters:

_.pluck(_.flatten(_.filter(_.groupBy(objects, "nums"), function(el) {
   return (el.length !== 1)
})), "name")

or a bit tidier

var hmap = _(objects).groupBy("nums").values();
var unique = hmap.where({'length': 1}).flatten().value();
var duplicates = hmap.flatten().difference(unique).value();

edited Jan 9, 2015 at 21:39

answered Jan 9, 2015 at 1:48

nullpotent

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1 Comment

Scotty Bollinger Over a year ago

Thanks and this is very close. However, Your solution assumes I know the value of "1" in the duplicates. In my real-world scenario, I will not know any of the values to filter by.

Barmar · Accepted Answer · 2015-01-09 18:49:50Z

0

I don't know underscore.js, here's how to do it with plain JS:

var counts = {};
var duplicates = [];
for (var i = 0; i < objects.length; i++) {
    var str = JSON.stringify(objects[i].nums);
    if (str in counts) {
        counts[str]++;
    } else {
        counts[str] = 1;
    }
}
objects = objects.filter(function(val) {
  if (counts[JSON.stringify(val.nums)] == 1) {
    return true;
  } else {
    duplicates.push(val.name);
    return false;
  }
});

DEMO

edited Jan 9, 2015 at 18:49

answered Jan 9, 2015 at 16:53

Barmar

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2 Comments

Scotty Bollinger Over a year ago

Thanks for the response, but it does not seem to work jsbin.com/bekuku/1/edit?js,console

Barmar Over a year ago

I fixed the problems. I was only saving one of the names in the duplicate.

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