mongoose - Add if not in array, remove if already in array

Question

What is the fastest way in mongoose to determine if an element is already in an array. In that case I want to delete the element from that array. In the case the array doesn't contain the specific element I want to add it.

Of course adding and removing can be done with addToSet and remove(_id). Querying is also no problem. I really care more about the shortest way to do this, with less effort.

For example I suggest to take the Schema:

var StackSchema = new Schema({
    references: [{ type: Schema.Types.ObjectId, ref: 'Person' }]
});

Let's say the the references array contains the elements:

['5146014632B69A212E000001',
 '5146014632B69A212E000002',
 '5146014632B69A212E000003']

Case 1: My method receives 5146014632B69A212E000002 (So this entry should be removed.)

Case 2: My method receives 5146014632B69A212E000004 (So this entry should be added.)

Hussein Nazzal · Accepted Answer · 2013-09-15 22:57:18Z

2

the solution for anyone passing by . :)

if(doc.references.indexOf(SOMESTRING) !== -1) {
    console.log('it\'s there') ; doc.likes.pull(SOMESTRING);
}else{
    doc.references.push(SOMESTRING);
}

answered Sep 15, 2013 at 22:57

Hussein Nazzal

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nevi_me · Accepted Answer · 2013-03-22 13:04:39Z

Here's the logic, with code below.

I normally use underscore.js for such tasks, but you could do it in just JavaScript.

fetch the document.
iterate through the _ids in the document, performing a truth test.
If the document has the _id that you're testing, delete the current index from the array.
If you've gone through the whole array and there's nothing in there, array.push() the _id. Then document.save()

That's the approach that I normally follow.

In underscore, it'd go something like this:

function matching(a,b) { // a should be your _id, and b the array/document
  var i;
  for ( i = 0, i < b.length , i++) {
    if ( a.toString() === b[i].toString() )
      return i;
    else return -1;
  }
};

Then you'd use the function thus:

var index = matching( '5146014632B69A212E000002', doc );
if ( index > -1 )
  doc.splice( index , 1);
else 
  doc.push( '5146014632B69A212E000002' );

score 0 · Accepted Answer · 2020-04-15 04:53:24Z

0

@Hussein answer, but using Lodash:

const _ = require("lodash")

const User = require("./model")

const movies = ["Inception", "Matrix"]

(async () => {
    // Catch errors here
    const user = User.findById("")

    const userMoviesToggle = _.xor(
        user.movies, // ["Inception"]
        movies
    ); // ["Matrix"]

    user.movies = userMoviesToggle

    // Catch errors here
    user.save()
})()

edited Apr 15, 2020 at 4:53

answered Apr 15, 2020 at 4:38

user7075574

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