Replace an array field value

Question

Consider the following mongo data:

{ _id: "1",
  names: ["John", "Peter"]
}

What is the correct way to replace a simple element in the array, getting the following result ?

{ _id: "1",
  names: ["John", "Sarah"]
}

In my code I receive a function to exchange "Peter" with "Sarah", like:

substituteItemOnArray = (id, from, to) => {
   MyModel.update({
      id: id
   },
   {
      ??? What is the correct way to substitute one element with another ???
   });

}

substituteItemOnArray("1", "Peter", "Sarah");

does names is an array of strings? something like names: ["John", "Peter"]. I believe data is also type of array — Prasad Telkikar
– Prasad Telkikar, Commented Feb 21, 2019 at 13:21
Possible duplicate of How to Update Multiple Array Elements in mongodb — Daksh M.
– Daksh M., Commented Feb 21, 2019 at 13:25

Ashh · Accepted Answer · 2019-02-21 16:07:33Z

1

Simply use $ positional operator

db.getCollection('test').findOneAndUpdate(
  { names: "Peter" },
  { $set: { 'names.$': "Sarah" }}
)

answered Feb 21, 2019 at 16:07

Ashh

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2 Comments

Mendes Over a year ago

Is this gonna work no matter "Sarah"'s positions on the array? ["John", "Sarah"], ["Sarah", "John"], ["John", "Sarah", "Peter"], etc.

Ashh Over a year ago

Yes you can check

Arif · Accepted Answer · 2019-02-21 13:28:00Z

1

I don't know any way to do it with just Mongo operators.

I think you will have to retrive the document by id, find the index of the string you want to replace and only after that update document

Below function should do what I described above

async substituteItemOnArray = (_id, from, to) => {
    const doc = await MyModel.findOne({  _id  });
    if (doc && doc.names && doc.names.indexOf(from) > -1) {

    const index = dox.names.indexOf(from); 
    const keyToUpdate = `names.${index}`;
    MyModel.update({ _id }, { $set: { [keyToUpdate] : to} },)
}

substituteItemOnArray("1", "Peter", "Sarah");

answered Feb 21, 2019 at 13:28

Arif

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Comments

Daksh M. · Accepted Answer · 2019-02-21 13:36:17Z

1

You can do this with mongoDB arrayFilters like this in mongoose:

function substituteItemOnArray = (id, from, to) {
  return MyModel.findOneAndUpdate(
    {id: id}, // where to update
    {$set: {'names.$[element]': to }}, // what to update
    {arrayFilters: [{'element': from}]} // what should match in array.
  )
}

(
  async () => {
    let doc = await substituteItemOnArray(id, "Peter", "Sarah");
    console.log(doc);
  }
)()

answered Feb 21, 2019 at 13:36

Daksh M.

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