How to filter an array that excludes from object's property array

Question

let project = {
    title: "some title",
    participants: [{
        _id: "12345678",
        name: "John"
    }, {
        _id: "44332211",
        name: "Jackson"
    }, {
        _id: "55667788",
        name: "Steve"
    }]
}

let users = [{
    _id: "12345678",
    name: "John"
}, {
    _id: "44332211",
    name: "Jackson"
}, {
    _id: "09876543",
    name: "Aaron"
}, {
    _id: "55667788",
    name: "Steve"
}, {
    _id: "22334455",
    name: "Xavier"
}]

How do I list out all the users that are NOT part of the project participants? includes does not work because project is an object...

Please visit help center, take tour to see what and How to Ask. Do some research, search for related topics on SO; if you get stuck, post a minimal reproducible example of your attempt, noting input and expected output, preferably in a Stacksnippet — mplungjan
– mplungjan, Commented Jun 12, 2020 at 18:05
@mplungjan I searched for related topic before I ask, and I tried their solution, does not work that's why I came here to ask for help — Lucas Chan
– Lucas Chan, Commented Jun 12, 2020 at 18:27

mickl · Accepted Answer · 2020-06-12 18:06:34Z

6

array.filter + array.some will work:

let project = {
    title: "some title",
    participants: [{
        _id: "12345678",
        name: "John"
    }, {
        _id: "44332211",
        name: "Jackson"
    }, {
        _id: "55667788",
        name: "Steve"
    }]
}

let users = [{
    _id: "12345678",
    name: "John"
}, {
    _id: "44332211",
    name: "Jackson"
}, {
    _id: "09876543",
    name: "Aaron"
}, {
    _id: "55667788",
    name: "Steve"
}, {
    _id: "22334455",
    name: "Xavier"
}]

let result = users.filter(user => !project.participants.some(p => p._id === user._id));
console.log(result);

answered Jun 12, 2020 at 18:06

mickl

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3 Comments

user2112618 Over a year ago

This is the same solution I was going to post until you did it, upvoted it.

Lucas Chan Over a year ago

thanks, I tried this filter + some function before I posted this question, it does not work on my actual code, when I console log project.partcipants[0]._id and users[0]._id, both has the same value, but it still evaluate as "false", guess I have to apply toString method to make it work

3limin4t0r Over a year ago

If the ids don't have the same type. For example one being an integer and on being a string you could also use == instead of ===.

Rajneesh · Accepted Answer · 2020-06-12 18:11:15Z

1

You can also make use of find with filter:

var users = [{ _id: "12345678", name: "John"}, { _id: "44332211", name: "Jackson"}, { _id: "09876543", name: "Aaron"}, { _id: "55667788", name: "Steve"}, { _id: "22334455", name: "Xavier"}];
var project = { title: "some title", participants: [{ _id: "12345678", name: "John" }, { _id: "44332211", name: "Jackson" }, { _id: "55667788", name: "Steve" }]};

var result = users.filter(k=>!project.participants.find(p=>p._id==k._id));

console.log(result);

answered Jun 12, 2020 at 18:11

Rajneesh

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Comments

Vignesh Raja · Accepted Answer · 2020-06-12 18:15:48Z

1

Using Array.map and Array.filter

let project = { title: "some title",
    participants: [{_id: "12345678", name: "John"},
    {_id: "44332211", name: "Jackson"},
    {_id: "55667788", name: "Steve"}]
}

let users = [{ _id: "12345678", name: "John"}, 
{ _id: "44332211", name: "Jackson"},
{ _id: "09876543", name: "Aaron"},
{ _id: "55667788", name: "Steve"},
{ _id: "22334455", name: "Xavier"}];

var participants = project.participants.map(function(p){ return p._id; })
var non_participants = users.filter(function(user){
  return participants.indexOf(user._id) == -1;
});
console.log(non_participants);

answered Jun 12, 2020 at 18:15

Vignesh Raja

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Comments

3limin4t0r · Accepted Answer · 2020-06-12 18:31:40Z

1

I would first extract the participant ids into a Set for fast lookup. Then filter the users and check if the id is not included in the set (using has).

let project = {
  title: "some title",
  participants: [
    { _id: "12345678", name: "John"    },
    { _id: "44332211", name: "Jackson" },
    { _id: "55667788", name: "Steve"   },
  ]
};
let users = [
  { _id: "12345678", name: "John"    },
  { _id: "44332211", name: "Jackson" },
  { _id: "09876543", name: "Aaron"   },
  { _id: "55667788", name: "Steve"   },
  { _id: "22334455", name: "Xavier"  },
];

const participantIds = new Set(project.participants.map(participant => participant._id));
const usersWithoutProject = users.filter(user => !participantIds.has(user._id));

console.log(usersWithoutProject);

edited Jun 12, 2020 at 18:31

answered Jun 12, 2020 at 18:25

3limin4t0r

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