Javascript return array from 2 arrays removing duplicates - Stack Overflow

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Searched and tried and no luck so far.

var newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ]

var likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ]

What I want returned is:

var leftUsers = [{name: 'lauren', id: 35}, {name: 'dave', id: 28} ]

basically without the rich object as this is a duplicate. I only care about the id key.

I have tried:

newUsers.forEach((nUser) => {
    likedUsers.forEach((lUser) => {
        if (nUser.id !== lUser.id){
            leftUsers.push(nUser)
        }
    })
})

but obviously this won't work as this will just add them all as soon as they don't match.

if possible would like an es6 solution using forEach/map/filter

thanks

Searched and tried and no luck so far.

var newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ]

var likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ]

What I want returned is:

var leftUsers = [{name: 'lauren', id: 35}, {name: 'dave', id: 28} ]

basically without the rich object as this is a duplicate. I only care about the id key.

I have tried:

newUsers.forEach((nUser) => {
    likedUsers.forEach((lUser) => {
        if (nUser.id !== lUser.id){
            leftUsers.push(nUser)
        }
    })
})

but obviously this won't work as this will just add them all as soon as they don't match.

if possible would like an es6 solution using forEach/map/filter

thanks

• javascript
• arrays
• ecmascript-6
• duplicates
• javascript-objects

Share Improve this question Follow edited Jan 31, 2018 at 10:32 The Walrus asked Jan 31, 2018 at 10:31 The WalrusThe Walrus 1,20877 gold badges3131 silver badges5050 bronze badges 9

• 1 Possible duplicate of How to merge two arrays in JavaScript and de-duplicate items – Serge K. Commented Jan 31, 2018 at 10:32
• @SergeK. well no coz this concerns objects, and 2 why are you downvoting me? – The Walrus Commented Jan 31, 2018 at 10:33
• 1 So, what happened to brian? You want only the items in new that aren't in liked? – Cerbrus Commented Jan 31, 2018 at 10:34
• 1 The logic is the same... You just have to change a[i] === a[j] to a[i].myProp === a[j].myProp. You could also find lot of example all over the internet. – Serge K. Commented Jan 31, 2018 at 10:35
• first merge it into one array, then loop it and save the ids in a new array var. always check the id doesnt exists in this new array and if it exists delete it on the merged one – David Commented Jan 31, 2018 at 10:35

 |  Show 4 more ments

4 Answers 4

Sorted by: Reset to default 7

With array.prototype.filter to filter out items that exists in likedUsers and array.prototype.findIndex to check the existence, it should be:

var newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ];
var likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ];

var leftUsers = newUsers.filter(u => likedUsers.findIndex(lu => lu.id === u.id) === -1);

console.log(leftUsers);

You can do this with filter() and some() methods.

var newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ]
var likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ]

const result = newUsers.filter(e => !likedUsers.some(a => a.id == e.id));
console.log(result)

var newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ];
var likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ];

var leftusers = newUsers.filter( item => !likedUsers.find(item2 => item.id == item2.id));

console.log(leftusers);

You can create a Set of ids that are found in likedUsers, and filter the newUsers by checking if an id is in the Set:

const newUsers = [{name: 'rich', id: 25}, {name: 'lauren', id: 35}, {name: 'dave', id: 28} ]
const likedUsers = [{name: 'derek', id: 39}, {name: 'rich', id: 25}, {name: 'brian', id: 38} ]

const result = newUsers.filter(function({ id }) {
  return !this.has(id) // take all users which ids is not found in the set
}, new Set(likedUsers.map(({ id }) => id))) // create a set of ids in likedUsers and assign to this

console.log(result)

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