How can I change the data type of a String field to [String] in MongoDB while retaining the previous data?

Question

MongoDB

I have a field with phone number phone. Currently, only one phone number can be stored there. But now we need to store several phone numbers, and I need to somehow write a migration for all this.

I tried

db.Clients.updateMany({}, {$set: { phones:  ["$phone"] } })

But instead of substituting the value from the field into the array as the first element phone, he simply substituted this string there.

Answer 1

db.Clients.find({}).forEach(el => {
    db.Clients.updateOne({ _id: el._id }, { $set: { phone: [el.phone] }})
})