Javascript Firebase身份验证加载页面的onAuthStateChanged中的重定向

我听从了老师的指示

index.html：

auth.js：

我可以看出，这段代码是一个无止境的循环。但我看不出我从说明书中漏掉了什么。似乎此说明应该有效。

当您调用该方法并成功时，用户已登录。所以，如果我正确理解了您的功能需求，您就不需要使用onAuthStateChanged

您可以按照以下思路做一些事情：

function login() {
    var email = document.getElementById('email').value;
    var password = document.getElementById('password').value;
    if (email.length < 4) {
        alert('Please enter an email address.');
        return;
    }
    if (password.length < 4) {
        alert('Please enter a password.');
        return;
    }

    firebase.auth().signInWithEmailAndPassword(email, password)
    .then(userCredential => {
       console.log("User " + userCredential.user.uid + " LOGGED IN");
       window.location = 'admin-console.html';
    })
    .catch(function (error) {
            var errorCode = error.code;
            var errorMessage = error.message;
            if (errorCode === 'auth/wrong-password') {
                alert('Wrong password.');
            } else {
                alert(errorMessage);
            }
            console.log(error);
            //Throw an error
        });
}

function logout() {
    firebase.auth().signOut()
    .then(() => {
       console.log("User SIGNED OUT");
       window.location = 'index.html';';
    })
}

function initApp() {
    console.log('start initApp');
    document.getElementById('loginbutton').addEventListener('click', login, false);
    document.getElementById('logoutbutton').addEventListener('click', logout, false);
}

window.onload = function () {
    console.log('initialize app');
    initApp();
};

请注意，您需要添加一个注销按钮。如果你只想有一个切换按钮，而不是一个登录按钮加上一个注销按钮，你可以很容易地修改上面的代码

function toggleSignIn() {
    if (firebase.auth().currentUser) {
        firebase.auth().signOut();
    } else {
        var email = document.getElementById('email').value;
        var password = document.getElementById('password').value;
        if (email.length < 4) {
            alert('Please enter an email address.');
            return;
        }
        if (password.length < 4) {
            alert('Please enter a password.');
            return;
        }
        firebase.auth().signInWithEmailAndPassword(email, password).catch(function (error) {
            var errorCode = error.code;
            var errorMessage = error.message;
            if (errorCode === 'auth/wrong-password') {
                alert('Wrong password.');
            } else {
                alert(errorMessage);
            }
            console.log(error);
        });
    }
}

function initApp() {
    console.log('start initApp');
    firebase.auth().onAuthStateChanged(function (user) {
        if (user) {
            console.log('logged in');
            window.location = 'admin-console.html';
        } else {
            console.log('not logged in');
            window.location = 'index.html'; //causes endless loop
        }
    });
    document.getElementById('loginbutton').addEventListener('click', toggleSignIn, false);
}

window.onload = function () {
    console.log('initialize app');
    initApp();
};

function login() {
    var email = document.getElementById('email').value;
    var password = document.getElementById('password').value;
    if (email.length < 4) {
        alert('Please enter an email address.');
        return;
    }
    if (password.length < 4) {
        alert('Please enter a password.');
        return;
    }

    firebase.auth().signInWithEmailAndPassword(email, password)
    .then(userCredential => {
       console.log("User " + userCredential.user.uid + " LOGGED IN");
       window.location = 'admin-console.html';
    })
    .catch(function (error) {
            var errorCode = error.code;
            var errorMessage = error.message;
            if (errorCode === 'auth/wrong-password') {
                alert('Wrong password.');
            } else {
                alert(errorMessage);
            }
            console.log(error);
            //Throw an error
        });
}

function logout() {
    firebase.auth().signOut()
    .then(() => {
       console.log("User SIGNED OUT");
       window.location = 'index.html';';
    })
}

function initApp() {
    console.log('start initApp');
    document.getElementById('loginbutton').addEventListener('click', login, false);
    document.getElementById('logoutbutton').addEventListener('click', logout, false);
}

window.onload = function () {
    console.log('initialize app');
    initApp();
};