GetEnvironmentVariable("key","default")
The solution in the link is to use Environmentvariables on the Serverside. You already got told that you can use
GetEnvironmentVariable("key","default")i think i agree with don manfred here. may be its not clear for you how the enviroment variables work.
if by client side you mean the browser then you can store cookies, the semi correct implementation is to encrypt those cookies with any encryption library and send it. The correct implementation is that the cookie is just a pointer to the real information on your server.
<!DOCTYPE html>
<html lang="pt-BR">
<head>
<meta charset="UTF-8">
<title>TodoList</title>
<link rel="shortcut icon" href="img/todoListFavicon.png" type="image/x-icon">
<link rel="stylesheet" href="css/styles.css">
</head>
<body>
<div id="app">
<!--Logotipo do TodoList-->
<div class="center">
<img src="img/todoList.png">
</div>
<!--Feedback de carregamento (loading)-->
<div id="loading">
<img src="img/loading.gif" alt="Animação de carregamento">
</div>
<!--Conteúdo destinado para usuários não autenticados-->
<div id="auth" class="center">
<!--Formulário de autenticação-->
<form id="authForm">
<h3 id="authFormTitle">Acesse a sua conta para continuar</h3>
<label for="email">E-mail: </label>
<input type="email" placeholder="E-mail" id="email">
<label for="password">Senha: </label>
<input type="password" placeholder="Senha" id="password">
<button type="submit" id="submitAuthForm">Acessar</button>
</form>
<!--Alternar o fomulário de autenticação para o cadastro de novas contas-->
<p id="register">
Não possui uma conta?
<button onclick="toggleToRegister()" class="alternative">Cadastrar uma nova conta</button>
</p>
<!--Alternar o fomulário de autenticação para o acesso de contas já existentes-->
<p id="access" class="startHidden">
Já possui uma conta?
<button onclick="toggleToAccess()" class="alternative">Acesse a sua conta</button>
</p>
</div>
</div>
<!--Recursos do Firebase-->
<script src="https://www.gstatic.com/firebasejs/7.8.1/firebase-app.js"></script>
<script src="https://www.gstatic.com/firebasejs/7.8.1/firebase-auth.js"></script>
<!-- LOADING FIREBASE.JS BELOW -->
<script src="js/firebase.js"></script>
<script src="js/utils.js"></script>
<script src="js/auth.js"></script>
</body>
</html>// Your web app's Firebase configuration
var firebaseConfig = {
apiKey: "AIzaSyCvEv7AropwWlIEC-w5c3JgprOPxjA8-kM", // b4j_env("myapikey")
authDomain: "todolist-84473.firebaseapp.com", // b4j_env("myauthdomain")
databaseURL: "https://todolist-84473.firebaseio.com", // b4j_env("dburl")
projectId: "todolist-84473", // b4j_env("myprojid")
storageBucket: "todolist-84473.appspot.com", // b4j_env("....")
messagingSenderId: "1009074245486", // b4j_env("....")
appId: "1:1009074245486:web:f573ce9d33c653b28ebb7f" // b4j_env("....")
};
// Initialize Firebase
firebase.initializeApp(firebaseConfig);
