MongoDB Change the data type of a field

Problem: I want to change the data type of a field in my MongoDB collection from string to Date.

Example: I have a field in my collection called expiry which has values stored in string like 31 Dec 2021 . I need to change this to a Date object.

Solution:

db.posts.find({}).forEach(function (doc) {
  db.posts.updateOne(
    {
      _id: doc._id,
    },
    {
      $set: {
        expiry: new Date(doc.expiry)
      },
    }
  )
})

The above shell command will find all collections in my posts collection and change the data in expiry field which is of type string to Date