money bot - new expense

addExpense.js

const Firebase = require("./firebase.init");

const addExpense = (request, res) => {
  const body = request.body;
  const UID = body["messenger user id"];
  const ref = Firebase.FireDB.ref(UID);
  ref.once("value").then(snapshot => {
    const user = snapshot.val() || "undefined";
    if (user !== "undefined") {
      const date = new Date();
      const month = date.getMonth();
      const monthExpense = ref.child(month);
      monthExpense.push({
        amount: body["expense"],
        poste: body["poste"]
      });
      let total = 0;
      const currentMonth = user[month];
      for (let i in currentMonth){
        total += parseInt(currentMonth[i].amount)
      }
      total += parseInt(body["expense"]);
      const answer = `Depuis le debut du mois tu as dépensé ${total} ₪`;
      const message = {"messages": [{"text": answer}]};
      res.send(message);
    }
  });
};

module.exports = { addExpense };