"use strict";
const
    mongodb = require("mongodb"),
    GridFSBucket = mongodb.GridFSBucket,
    MongoClient = mongodb.MongoClient,
    fs = require("fs");

MongoClient.connect("mongodb://localhost:27017/test").then(function (db) {
    const bucket = new GridFSBucket(db),
        readStream = fs.createReadStream("./bigfile.dat"),
        uploadStream = bucket.openUploadStream("bigfile.dat"),
    uploadStream.once("finish", function () {
        console.log(uploadStream.id);
    });

    readStream.pipe(uploadStream);
});