Check if Facebook JS-API app already has been given permission - facebook

Question

I have a small script that unlocks some content on a page when a user logs in via Facebook and posts some information on their wall.
I want to avoid any duplicate posts (spam) in the event the user visits the page a second time and repeats the process.
Is there a way of (when asking for the permissions) to tell if they have already been given and therefore skip the sharing part of the script?
Here's my code:
$('.preview a').click(function(e) {
e.preventDefault();
FB.login(function(response) {
if (response.session) {
FB.api('/me/feed', 'post', {
message: 'Just unlocked the exclusive preview of...',
picture: 'http://website.com/share.png',
link: 'http://www.website.com',
name: 'Name goes here',
description: 'Description here'
},
function(response) {
if (!response || response.error) {
alert(response.error);
} else {
$('.preview').hide();
$('.clip').show();
}
});
}
},
{perms:'read_stream,publish_stream'});
});

Answer 1

From 2011 to 2014 a lot of things change..
I made this solution to check for "user_friends" and "publish_actions" permissions, if not allowed the both, force the user to "re-autenticate". The callback method will only be called when all permissions are given.
function login(cb,forceAuth) {
FB.getLoginStatus(function (response) {
if (response.status !== 'connected' || forceAuth==true){
FB.login(function (response) {
checkPermissions(cb,false);
}, {scope: 'publish_actions,user_friends'});
} else {
checkPermissions(cb);
}
});
}
function checkPermissions(cb,forceAuth){
FB.api(
"/me/permissions",
function (response) {
if (response.data[0]['publish_actions']==undefined || response.data[0]['publish_actions']==0 ||
response.data[0]['user_friends']==undefined || response.data[0]['user_friends']==0) {
if (forceAuth!=false)
login(cb,true);
} else {
cb();
}
}
);
}
How to use:
login(function () {
myLogedAndAllowedFunction();
});

Answer 2

I've written a tutorial about this here, and here's an example:
FB.api({ method: 'fql.query', query: 'SELECT read_stream,offline_access,publish_stream FROM permissions WHERE uid=me()' }, function(resp) {
for(var key in resp[0]) {
if(resp[0][key] === "1")
console.log(key+' is granted')
else
console.log(key+' is not granted')
}
});
There's also a JS REST example there in the article just for reference.