I am implementing Google log in for the first time as described here and here.
I am using HTML with Javascript.
The problem that needs solving is as follows: How can I, after the initial login, on a different page (say a landing page, or portal that the user sees after logging in), check if the user is logged in? Is there a service I can call to check the user’s login in status with my app key or something similar? I assume I would have to include the google API on each page.
Login Page Code:
Script In Head (Code from Google’s tutorial listed above):
<head>
....
<script src="https://apis.google.com/js/platform.js" async defer></script>
<script>
function onSignIn(googleUser)
{
var profile = googleUser.getBasicProfile();
console.log('ID: ' + profile.getId());
console.log('Name: ' + profile.getName());
console.log('Image URL: ' + profile.getImageUrl());
console.log('Email: ' + profile.getEmail());
alert(profile.getName());
}
function logout()
{
alert('logging out');
var auth2 = gapi.auth2.getAuthInstance();
auth2.signOut().then(function () {
console.log('User signed out.');
});
}
...
</head>
Code In Body (1st line from Google’s tutorial listed above, 2nd line to trigger logout test)
<body> ... <div class="g-signin2" data-onsuccess="onSignIn"></div> <div onmousedown="logout()">Logout</div> ... </body>
Is there some way I can include the google API on another page, and then call some check login status function? Or another way to concretely tell if the user is logged in or out?
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Answer
You can stringify a custom userEntity object and store it in sessionStorage where you can check it anytime you load a new page. I have not tested the following but it should work (doing something similar with WebAPI tokens in the same way)
function onSignIn(googleUser)
{
var profile = googleUser.getBasicProfile();
console.log('ID: ' + profile.getId());
console.log('Name: ' + profile.getName());
console.log('Image URL: ' + profile.getImageUrl());
console.log('Email: ' + profile.getEmail());
var myUserEntity = {};
myUserEntity.Id = profile.getId();
myUserEntity.Name = profile.getName();
//Store the entity object in sessionStorage where it will be accessible from all pages of your site.
sessionStorage.setItem('myUserEntity',JSON.stringify(myUserEntity));
alert(profile.getName());
}
function checkIfLoggedIn()
{
if(sessionStorage.getItem('myUserEntity') == null){
//Redirect to login page, no user entity available in sessionStorage
window.location.href='Login.html';
} else {
//User already logged in
var userEntity = {};
userEntity = JSON.parse(sessionStorage.getItem('myUserEntity'));
...
DoWhatever();
}
}
function logout()
{
//Don't forget to clear sessionStorage when user logs out
sessionStorage.clear();
}Of course, you can have some internal checks if the sessionStorage object is tampered with. This approach should work with modern browsers like Chrome and Firefox.