I want to get data from the database. Then change them. And then display. Please tell me how to solve this problem and why I can not do it. Here is my code
let firebaseConfig = {...}; firebase.initializeApp(firebaseConfig); let ref = firebase.database().ref('/data') class DataTable { constructor(parent) { this.parent = parent; } buildTable(data) { this.data = data; const keys = Object.keys(data[0]); console.log(keys) let div = document.createElement('div'); let tab = document.createElement('table'); let tb = document.createElement('tbody'); const buildTableBody = () => { for (let a of data) { let tr = document.createElement('tr'); keys.forEach((key) => { let td = document.createElement('td'); let tn = document.createTextNode(a[key]) td.appendChild(tn); tr.appendChild(td); }); tb.appendChild(tr); } tab.appendChild(tb); div.appendChild(tab); } this.parent.appendChild(div); buildTableBody() } } const table = new DataTable(document.body); table.buildTable( ref.once("value").then((snap) => { const data = snap.val() data.map(i => { let res = { '#': Number(i.id), 'Name': i.name, }; return Object.entries(res).reduce((memo, [key, value]) => { if (value) { return { ...memo, [key]: value } } else { return memo; } }, {}) }) })) But it returns to me Promise {}proto: Promise[[PromiseStatus]]: "resolved"[[PromiseValue]]: undefined
