In Firestore node.js, set the max value on a field similar to https://cloud.google.com/firestore/docs/reference/rest/v1/Write#FieldTransform

max.js

import firebase from "firebase/app";
import "firebase/firestore";

const randomNumber = Math.floor(Math.random() * 1000);

const docRef = firebase.firestore.doc("path/to/doc");
db.runTransaction(async function(t) {
  const doc = await t.get(docRef);
  if (doc.exists && doc.data().number < randomNumber) {
    console.log("setting new max");
    t.update(docRef, { number: randomNumber });
  }
});