How to delete documents by field?

Question

JavaScript

Hello, such a question arose, I began to familiarize myself with the node js express + mongodb technology stack (I exclude mongoose for now, I say right away to exclude questions about it).
There is a users database, it contains the user collection, it contains documents with the following fields:

{
                "_id" : ObjectId("5d8342f4b172fcb285fc597a"),
                "name" : "Andrey",
                "age" : 32,
                "sex" : {
                        "male" : true,
                        "female" : false
                }
        },
        {
                "_id" : ObjectId("5d834329b172fcb285fc597c"),
                "name" : "Anna",
                "age" : 48,
                "sex" : {
                        "male" : false,
                        "female" : true
                }
        },
        {
                "_id" : ObjectId("5d8369c1b172fcb285fc597e"),
                "name" : "Anna",
                "age" : 48,
                "postIndex" : 67890
        },
        {
                "_id" : ObjectId("5d8369d4b172fcb285fc597f"),
                "name" : "Andrey",
                "age" : 48,
                "postIndex" : 123456
        },
        {
                "_id" : ObjectId("5d836bb2b172fcb285fc5980"),
                "name" : "Anton",
                "age" : 48,
                "postIndex" : "123456"
        },
        {
                "_id" : ObjectId("5d836c52b172fcb285fc5981"),
                "name" : "Annete",
                "age" : 48,
                "postIndex" : -1975
        },
        {
                "_id" : ObjectId("5d836e91b172fcb285fc5982"),
                "name" : "Annete",
                "age" : 48,
                "postIndex" : 0.0016502834182392193
        },
        {
                "_id" : ObjectId("5d836ec6b172fcb285fc5983"),
                "name" : "Annete",
                "age" : 48,
                "postIndex" : ISODate("2019-09-19T12:04:22.380Z")
        }

I would like to remove all documents that have a postIndex field, no matter what value they have.
I understand that in order to delete all documents that have this field with INTEGRATE values, you need to write the following on the server:

db.user.remove($where:"/[0-9]+/.test(this.postIndex)")

I am interested in two questions, since I did not find answers to them (I rummaged through everything, including both Google and the doc):
1. How can I execute the same command on Node JS Express to delete with integer values?
2. How can I delete a document in the collection on the server and on Node JS Express by its presence of any field? (in this example, postIndex)
I would be grateful for any answers, comments, or even just tips on solving this problem.