Facebook Authentication - adding permission for accessing email address - email

Question

It might be a basic question.
And also my English is poor...
I have a web service which needs Facebook login.
With JavaScript SDK, I can get users' basic information such as user ID, name, gender.
And now there are about 10000 users.
This time, I need to access users' email address.
I know I can get email address from new users by adding scope attribute.
However, from existed users, though I can access email address, I don't know how to display authorization dialogue for permission to access email address.
Any idea? Thanks in advance!

Answer 1

Below is a code snippet that I have used. Basically check their permissions using /me/permissions and show a reauthenticate link
<script>
var FB_config = {
API_ID: 123123123123,
PERMISSIONS: "publish_stream,email",
};
jQuery(document).ready(function(){
// initialise FB
window.fbAsyncInit = function() {
FB.init({
appId : FB_config.API_ID,
status : true,
cookie : true,
xfbml : true,
oauth : true
});
FB.Event.subscribe('auth.statusChange', FBverifyLogin);
};
});
function FBverifyLogin(response) {
if (response.status === 'connected') {
checkPermissions(); // check permissions if the user is logged in
}
}
function checkPermissions(){
jQuery("#FBreauth").hide();
FB.api('/me/permissions', function(response) {
var permissions = FB_config.PERMISSIONS.split(",");
for(var i = 0; i < permissions.length; i++)
{
if(response.data[0][permissions[i]] == undefined || response.data[0][permissions[i]] != 1)
{
// user does not have full permissions, show reauth link
jQuery("#FBreauth").show();
break;
}
}
});
}
function FBreauth(){
FB.ui(
{
method: 'oauth',
display: 'popup',
app_id: FB_config.API_ID,
client_id: FB_config.API_ID,
redirect_uri: "http://www.facebook.com/connect/login_success.html",
scope: FB_config.PERMISSIONS
}
);
}
</script>
App permissions have changes. Please reauthorize this app