Schedule cloud function to update a list of maps

I’m trying to write a scheduled cloud function to reset the value of “status” every day at 12 am. Here’s my firestore structure:
Firestore Data

I haven’t really tried coding in javascript before but here’s what I managed with my little knowledge:

const functions = require("firebase-functions");

const admin = require("firebase-admin");
admin.initializeApp();

const database = admin.firestore();


exports.Rst = functions.pubsub.schedule("0 0 * * *").onRun((context) => {
  const alist =
      database.collection("SA1XAoC2A7RYRBeAueuBL92TJEk1")
          .doc("afternoon").get().then((snapshot)=>snapshot.data["list"]);

  for (let i=0; i<alist.length; i++) {
    alist[i]["status"]=0;
  }

  database.collection("SA1XAoC2A7RYRBeAueuBL92TJEk1")
      .doc("afternoon").update({
        "list": alist,
      });

  return null;
});

I get the following error when I deploy this function:
Error

Expected Result:
Set the values of all “status” fields to 0.
Expected result