Firebase: Uncaught TypeError: Cannot read property 'signInWithEmailAndPassword'
问题 I'm doing simple signup by following YT tuts, link (https://www.youtube.com/watch?v=-OKrloDzGpU) There i have this script in app.js and i'm getting error Uncaught TypeError: Cannot read property 'signInWithEmailAndPassword' of undefined at HTMLInputElement.btnLogin.addEventListener.e (app.js:26) // GET Users info const txtEmail = document.getElementById('txtEmail'); const txtPassword = document.getElementById('txtPassword'); const btnLogin = document.getElementById('btnLogin'); const