Google sign-in using Javascript API without triggering popup

Question

I am using following code for users to be able to login using their Google account via Javascript API.

HTML

<a id="gp_login" href="javascript:void(0)" onclick="javascript:googleAuth()">Login using Google</a>

Javascript

function gPOnLoad(){
     // G+ api loaded
     document.getElementById('gp_login').style.display = 'block';
}
function googleAuth() {
    gapi.auth.signIn({
        callback: gPSignInCallback,
        clientid: googleKey,
        cookiepolicy: "single_host_origin",
        requestvisibleactions: "http://schema.org/AddAction",
        scope: "https://www.googleapis.com/auth/plus.login email"
    })
}

function gPSignInCallback(e) {
    if (e["status"]["signed_in"]) {
        gapi.client.load("plus", "v1", function() {
            if (e["access_token"]) {
                getProfile()
            } else if (e["error"]) {
                console.log("There was an error: " + e["error"])
            }
        })
    } else {
        console.log("Sign-in state: " + e["error"])
    }
}

function getProfile() {
    var e = gapi.client.plus.people.get({
        userId: "me"
    });
    e.execute(function(e) {
        if (e.error) {
            console.log(e.message);
            return
        } else if (e.id) {
            // save profile data
        }
    })
}(function() {
    var e = document.createElement("script");
    e.type = "text/javascript";
    e.async = true;
    e.src = "https://apis.google.com/js/client:platform.js?onload=gPOnLoad";
    var t = document.getElementsByTagName("script")[0];
    t.parentNode.insertBefore(e, t)
})()

This code is working fine. I want to use the above code (using Javascript) to login user from their Google account without triggering a popup window. Like, user clicks the login link, asked for app permissions in the same window/tab, user grants permission, user redirected back to the page where Google login link was, profile data is saved and user is logged in.

Answer 1

You can the use ux_mode parameter (options are 'redirect' or 'popup') and set a redirect_uri if you want to redirect to a different page.

It's also necessary to authorize the URL for the OAuth client on your google project page.

  function initClient() {
    gapi.client.init({
      apiKey: API_KEY,
      clientId: CLIENT_ID,
      discoveryDocs: DISCOVERY_DOCS,
      scope: SCOPES,
      ux_mode: 'redirect',
      //redirect_uri: custom url to redirect'
    }).then(function () {
      // Listen for sign-in state changes.
      gapi.auth2.getAuthInstance().isSignedIn.listen(updateSigninStatus);

      // Handle the initial sign-in state.
      updateSigninStatus(gapi.auth2.getAuthInstance().isSignedIn.get());
      authorizeButton.onclick = handleAuthClick;
      signoutButton.onclick = handleSignoutClick;
    });
  }

Answer 2

Such functionality is not provided through Google API. You should stick with gapi.auth.signIn. I know just one way to make it work, but it's very hacky.

gapi.auth.signIn opens authentication window. Save authentication window url in your app¹. Instead of calling gapi.auth.signIn, redirect user to that url.

To redirect successful authentication back to your website, add/modify redirect_url param in the url². Keep in mind that redirect_uri must be registered in developers console.

Example: https://accounts.google.com/o/oauth2/auth?client_id=1234567890.apps.googleusercontent.com&scope=https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fplus.login&immediate=false&response_type=token&redirect_uri=http://example.com

This way google will redirect user back to your website. access_token is provided through GET params.

¹If google changes their API this may break (since this method bypasses JS API and assumes that all those params in the url will be supported for ever).

²Redirect_url is introduced in offline access flow documentation. I don't think this param was intended to work in any other cases.

I strongly advise not to use this idea (since it bypasses JS API and uses undocumented functionality). Stick with gapi.auth.signIn.