Remove duplicates from Array of Array (nested array of objects)

Question

I have an Array which holds another Array of objects. I would like to remove the duplicates in this array of array.

var arr1 = [{
     child: [{name: "google", check: false}, {name: "yahoo", check: false}]
    },
    {
     child: [{name: "excite", check: false}, {name: "facebook", check: false}]
    },
    {
     child: [{name: "something1", check: false}, {name: "something2", check: false}]
    }
]

var arr2 = [{
     child: [{name: "google", check: true}, {name: "yahoo", check: false}]
    },
    {
     child: [{name: "excite", check: false}, {name: "facebook", check: false}]
    } 
]

var arr3 = [{
     child: [{name: "google", check: true}, {name: "yahoo", check: false}]
    },
    {
     child: [{name: "excite", check: false}, {name: "facebook", check: false}]
    },
    {
     child: [{name: "something1", check: false}, {name: "something2", check: false}]
    }
]

I would like to remove {name: "google", check: false} from the second child array as there is already one with same name and check: true in arr1.

Below is something what i have tried.

function mergeAndRemoveDuplicates(arr1, arr2) {

    return arr1.map(function(child) {
        return child.some(function(children) {
            return arr2.map(function(child2) {
                return child2.some(function(children2) {
                    return children.name === children2.name &&
                        children.check === true;
                });
            })
        })
    })
}

console.log(mergeAndRemoveDuplicates(arr1, arr2));

http://jsfiddle.net/g7rvbpf3/

@FlashThunder We don't always get to choose our data. Even if we did, there's likely a nicer way to ask the same question. — Dave Newton
– Dave Newton, Commented Mar 4, 2019 at 14:07
Remove {name: "google", check: false} from the arr2 as its already there in arr1 and merge arr1 and arr2. — Thalapathy
– Thalapathy, Commented Mar 4, 2019 at 14:15
For what I'm looking after the update, it appears that you want to update the data of arr1 with the new upcoming data from arr2. Is that what you really want? — Shidersz
– Shidersz, Commented Mar 4, 2019 at 15:43

Jonas Wilms · Accepted Answer · 2019-03-04 14:22:17Z

3

You could create a set of checked names and recursively filter the arrays:

const dupes = new Set;

for(const el of arr1.concat(arr2))
  el.child = el.child.filter(el => {
     const dupe = dupes.has(el.name);
     if(el.check) dupes.add(el.name);
     return !dupe;
  });

This will also filter duplicates in arr1, if that isn't wanted you could use arr1 to build up the set, and filter arr2:

 const dupes = new Set;

 for(const child of arr1.flatMap(it => it.child))
   if(child.checked) dupes.add(child.name);

for(const el of arr2)
 el.child = el.child.filter(it => !dupes.has(it.name));

To get one array at the end (I guess thats what you mean with "merge") you could just .concat one to the other.

edited Mar 4, 2019 at 14:22

answered Mar 4, 2019 at 14:06

Jonas Wilms

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2 Comments

Thalapathy Over a year ago

jsfiddle.net/t1zkLq53/1 seems flatMap is not available.... should i include any package like rxjs?

Jonas Wilms Over a year ago

@thalapathy It is ESnext, some browsers might not yet support it, however its just syntactic sugar for a nested loop in this case for(const el of arr1) for(const child of el.child) would work too here.

Shidersz · Accepted Answer · 2019-03-04 18:04:15Z

2

Understanding that you want to update the check properties of the elements in arr1 based on the new upcoming data from arr2, one possible approach can be to first create a hash table between the new upcoming name and check values. For this part we use Array.reduce(). The second part of the approach consiste of Array.map() the elements of the arr1 to hold the new updates.

var arr1 = [
    {
     child: [{name: "google", check: false}, {name: "yahoo", check: false}]
    },
    {
     child: [{name: "excite", check: false}, {name: "facebook", check: false}]
    },
    {
     child: [{name: "something1", check: false}, {name: "something2", check: false}]
    }
];

var arr2 = [
    {
     child: [{name: "google", check: true}, {name: "yahoo", check: false}]
    },
    {
     child: [{name: "excite", check: false}, {name: "facebook", check: false}]
    } 
];

let upHashTable = arr2.reduce((acc, {child}) =>
{
    child.forEach(({name, check}) => acc[name] = check);
    return acc;
}, {});

console.log("HashTable with updates: ", upHashTable);

let updated = arr1.map(({child}) =>
{
    return {child: child.map(o =>
    {
        o.check = upHashTable.hasOwnProperty(o.name) ? upHashTable[o.name] : o.check;
        return o;
    })};
});

console.log("Updated arr1 is: ", updated);

.as-console {background-color:black !important; color:lime;}
.as-console-wrapper {max-height:100% !important; top:0;}

Note this will only update values on arr1 and will not insert any new elements on it.

edited Mar 4, 2019 at 18:04

answered Mar 4, 2019 at 17:37

Shidersz

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2 Comments

Thalapathy Over a year ago

Thanks, but the output is array containing another array of objects... instead array of objects ... like below... var arr3 = [{ child: [{name: "google", check: true}, {name: "yahoo", check: false}] }, { child: [{name: "excite", check: false}, {name: "facebook", check: false}] }, { child: [{name: "something1", check: false}, {name: "something2", check: false}] } ]

Shidersz Over a year ago

@Thalapathy, sorry, I missed that part, I just updated to contemplate it.

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