Poseidon, whom she loved in return, she forgot her vows, and became united to him in marriage. For this offence she was punished by the goddess in a most terrible manner. Each wavy lock of the beautiful hair which had so charmed her husband, was changed into a venomous snake; her once gentle, love-inspiring eyes now became blood-shot, furious orbs, which excited fear and disgust in the mind of the beholder; whilst her former roseate hue and milk-white skin assumed a loathsome greenish tinge.
Athena
....
}
}
});
// Now that we've initialized the JavaScript SDK, we call
// FB.getLoginStatus(). This function gets the state of the
// person visiting this page and can return one of three states to
// the callback you provide. They can be:
//
// 1. Logged into your app ('connected')
// 2. Logged into Facebook, but not your app ('not_authorized')
// 3. Not logged into Facebook and can't tell if they are logged into
// your app or not.
//
// These three cases are handled in the callback function.
FB.getLoginStatus(function(response) {
statusChangeCallback(response);
});
};
// Load the SDK asynchronously
(function(d, s, id) {
var js, fjs = d.getElementsByTagName(s)[0];
if (d.getElementById(id)) return;
js = d.createElement(s); js.id = id;
js.src = "//connect.facebook.net/en_US/sdk.js";
fjs.parentNode.insertBefore(js, fjs);
}(document, 'script', 'facebook-jssdk'));
// Here we run a very simple test of the Graph API after login is
// successful. See statusChangeCallback() for when this call is made.
function testAPI() {
console.log('Welcome! Fetching your information.... ');
FB.api('/me', function(response) {
console.log('Successful login for: ' + response.name);
document.getElementById('status').innerHTML =
'Thanks for logging in, ' + response.name + '!';
});
}
Now you can test your app by going to the URL where you uploaded this HTML. Open your JavaScript console, and you'll see the testAPI() function display a message with your name in the console log.
Congratulations, at this stage you've actually built a really basic page with Facebook Login. You can use this as the starting point for your own app, but it will be useful to read on and understand what is happening in the code above.
Steps for Using Facebook Login With the JavaScript SDK
There are a few steps that you will need to follow to integrate Facebook Login into your web application, most of which are included in the quickstart example at the top of this page. At a high level those are:
Checking the login status to see if someone's already logged into your app. During this step, you also should check to see if someone has previously logged into your app, but is not currently logged in.
If they are not logged in, invoke the login dialog and ask for a set of data permissions.
Verify their identity.
Store the resulting access token.
Make API calls.
Log out.
Checking login status
The first step when loading your web page is figuring out if a person is already logged into your app with Facebook login. You start that process with a call to FB.getLoginStatus. That function will trigger a call to Facebook to get the login status and call your callback function with the results.
Taken from the sample code above, here's some of the code that's run during page load to check a person's login status:
FB.getLoginStatus(function(response) {
statusChangeCallback(response);
});
The response object that's provided to your callback contains a number of fields:
{
status: 'connected',
authResponse: {
accessToken: '...',
expiresIn:'...',
signedRequest:'...',
userID:'...'
}
}
status specifies the login status of the person using the app. The status can be one of the following:
connected. The person is logged into Facebook, and has logged into your app.
not_authorized. The person is logged into Facebook, but has not logged into your app.
unknown. The person is not logged into Facebook, so you don't know if they've logged into your app. Or FB.logout() was called before and therefore, it cannot connect to Facebook.
authResponse is included if the status is connected and is made up of the following:
accessToken. Contains an access token for the person using the app.
expiresIn. Indicates the UNIX time when the token expires and needs to be renewed.
signedRequest. A signed parameter that contains information about the person using the app.
userID is the ID of the person using the app.
Once your app knows the login status of the person using it, it can do one of the following:
If the person is logged into Facebook and your app, redirect them to your app's logged in experience.
If the person isn't logged into your app, or isn't logged into Facebook, prompt them with the Login dialog with FB.login() or show them the Login Button.
Logging people in
If people using your app aren't logged into your app or not logged into Facebook, you can use the Login dialog to prompt them to do both. Various versions of the dialog are shown below.
If they aren't logged into Facebook, they'll first be prompted to log in and then move on to logging in to your app. The JavaScript SDK automatically detects this, so you don't need to do anything extra to enable this behavior.
There are two ways to log someone in:
Use the Login Button.
Use FB.login() from the JavaScript SDK.
Using the Login Button
Including the Login Button into your page is easy. Visit the documentation for the login button and set the button up the way you want. Then click Get Code and it will show you the code you need to display the button on your page.
Note that in the example at the start of this document, we use the onlogin attribute on the button to set up a JavaScript callback that checks the login status to see if the person logged in successfully:
This is the callback. It calls FB.getLoginStatus() to get the most recent login state. (statusChangeCallback() is a function that's part of the example that processes the response.)
function checkLoginState() {
FB.getLoginStatus(function(response) {
statusChangeCallback(response);
});
}
Invoking the Login Dialog with the JavaScript SDK
For apps that want to use their own button, you can invoke the Login Dialog with a simple call to FB.login():
FB.login(function(response){
// Handle the response object, like in statusChangeCallback() in our demo
// code.
});
As noted in the reference docs for this function, it results in a popup window showing the Login dialog, and therefore should only be invoked as a result of someone clicking an HTML button (so that the popup isn't blocked by browsers).
There is an optional scope parameter that can be passed along with the function call that is a comma separated list of permissions to request from the person using the app. Here's how you would call FB.login() with the same scope as the Login Button we used above. In this case, it would ask for a person's email address and a list of friends who also use the app:
FB.login(function(response) {
// handle the response
}, {scope: 'public_profile,email'});
Handling Login dialog response
At this point in the login flow, your app displays the Login dialog, which gives people the choice of whether to cancel or to enable the app to access their data.
Whatever choice people make, the browser returns to the app and response data indicating whether they're connected or cancelled is sent to your app. When your app uses the JavaScript SDK, it returns an authResponse object to the callback specified when you made the FB.login() call:
This response can be detected and handled within the FB.login call, like this:
FB.login(function(response) {
if (response.status === 'connected') {
// Logged into your app and Facebook.
} else if (response.status === 'not_authorized') {
// The person is logged into Facebook, but not your app.
} else {
// The person is not logged into Facebook, so we're not sure if
// they are logged into this app or not.
}
});
Asking for Permissions
One of the most important parts of launching the Login Dialog is choosing what data your app would like access to. These examples have all used the scope parameter, which is how you ask for access to someone's data. These are all called Permissions.
Permissions are covered in depth in our permissions guide. However, there are a few things to remember when dealing with permissions and the login dialog:
You ask for permissions when the dialog is created. The resulting set of permissions is tied to the access token that's returned.
Other platforms may have a different set of permissions. For example, on iOS you can ask for places a person's been tagged, while in the web version of your app that permission is not required for the experience.
You can add permissions later when you need more capabilities. When you need a new permission, you simply add the permission you need to the list you've already granted, re-launch the Login Dialog and it will ask for the new permission.
The Login Dialog lets people decline to share certain permissions with your app that you ask for. Your app should handle this case. Learn more about this in our permissions dialog.
Apps that ask for more than public_profile, email and user_friends must be reviewed by Facebook before they can be made available to the general public. Learn more in our documentation for login review and our general review guidelines.
Storing Access Tokens
At the end of the login process, an access token is generated. This access token is the thing that's passed along with every API call as proof that the call was made by a specific person from a specific app.
The Facebook SDK for JavaScript automatically handles access token storage and tracking of login status in the browser, so nothing is needed for you to store access tokens in the browser itself.
However, a common pattern is to take the access token and pass it back to a server and the server makes calls on behalf of a person. In order to get the token from the browser you can use the response object that's returned via FB.getLoginStatus():
FB.getLoginStatus(function(response) {
if (response.status === 'connected') {
console.log(response.authResponse.accessToken);
}
});
The token is an opaque string of variable length.
Also keep in mind that the access tokens that are generated in browsers generally have a lifetime of only a couple of hours and are automatically refreshed by the JavaScript SDK. If you are making calls from a server, you will need to generate a long lived token, which is covered at length in our access token documentation.
Verifying identity
Apps normally need to confirm that the response from the Login dialog was made from the same person who started it. If you're using Facebook's JavaScript SDK it automatically performs these checks so nothing is required, assuming that you're only making calls from the browser.
If you decide to send it back to the server, you should make sure you re-verify the access token once it gets to the server. Re-verifying the token is covered in our documentation on manually building login flows. You'll need to verify that the app_id and user_id match what you expected from the access token debug endpoint.
Make API calls
At this point in the flow, the person is authenticated and logged in. Your app is now ready to make API calls on their behalf from the browser. In the browser, the easiest way to do that is with the FB.api() call. FB.api() will automatically add the access token to the call.
This code:
FB.api('/me', function(response) {
console.log(JSON.stringify(response));
});
Will return an array of values:
{
"id":"101540562372987329832845483",
"email":"example@example.com",
"first_name":"Bob",
[ ... ]
}
If you're making calls server side with the access token, you can use an SDK on the server to make similar calls. Many people use PHP to build web applications. You can find some examples of making server-side API calls in our PHP SDK documentation.
Logging people out
You can log people out of your app by attaching the JavaScript SDK function FB.logout to a button or a link, as follows:
FB.logout(function(response) {
// Person is now logged out
});
Note: This function call may also log the person out of Facebook. Consider the 3 scenarios below:
A person logs into Facebook, then logs into your app. Upon logging out from your app, the person is still logged into Facebook.
A person logs into your app and into Facebook as part of your app's login flow. Upon logging out from your app, the user is also logged out of Facebook.
A person logs into another app and into Facebook as part of the other app's login flow, then logs into your app. Upon logging out from either app, the user is logged out of Facebook.
Additionally, logging out is not the same as revoking login permission (removing previously granted authentication), which can be performed separately. Because of this your app should be built in such a way that it doesn't automatically force people who have logged out back to the Login dialog.
Adding Permissions
One of the best practices with Facebook Login is to not request read permissions and publishing permissions at the same time. To support this your app can ask for more permissions later, well after someone has logged in. To do that, all you have to do is launch the Login Dialog with the new permission that you're asking for.
For example, let's say you had a Login Button with the following permissions:
The dialog would look like this:
And if you checked /me/permissions for permissions granted after the person accepted you would find this:
{"data":
[
{
"permission":"public_profile",
"status":"granted"
},
{
"permission":"email",
"status":"granted"
}
]
}
If you wanted to add the user_friends permission later, you could re-launch it with the FB.login() function like this:
FB.login(function(response) {
console.log(response);
}, {scope: 'user_friends'});
(This function must be called from a button's event handler otherwise it's likely to be blocked by browser popup blockers.)
The dialog that it generates looks like this:
Note that it only asks for the new permission. If you accept the new permission checking /me/permissions will result in this:
{"data":
[
{
"permission":"public_profile",
"status":"granted"
},
{
"permission":"email",
"status":"granted"
},
{
"permission":"user_friends",
"status":"granted"
}
]
}
Note that the new user_friends permission has been added to the list of allowed permissions.
Re-asking for Declined Permissions
Facebook Login lets people decline sharing some permissions with your app. The Login Dialog contains a screen that looks like this:
The public_profile permission is always required and greyed out because it can't be disabled.
However, if someone were to uncheck user_likes (Likes) in this example, checking /me/permissions for what permissions have been granted results in:
{
"data":
[
{
"permission":"public_profile",
"status":"granted"
},
{
"permission":"user_likes",
"status":"declined"
}
]
}
Note that user_likes has been declined instead of granted.
It's OK to ask a person once to grant your app permissions that they've declined. You should have a screen of education on why you think they should grant the permission to you and then re-ask. But if you use the method described in the [previous section)(#re-launching-permissions-dialog) the Login Dialog won't ask for that permission.
This is because once someone has declined a permission, the Login Dialog will not re-ask them for it unless you explicitly tell the dialog you're re-asking for a declined permission.
You do this by adding the auth_type: rerequest flag to your FB.login() call:
FB.login(
function(response) {
console.log(response);
},
{
scope: 'user_likes',
auth_type: 'rerequest'
}
);
When you do that, the Login Dialog will re-ask for the declined permission. The dialog will look very much like the dialog in the section on re-asking for permissions but will let you re-ask for a declined permission.
Detecting when people uninstall apps
People are able to uninstall apps via Facebook.com without interacting with the app itself. To help apps detect when this has happened, we allow them to provide a de-authorize callback URL which will be pinged whenever this occurs.
You can enable a deauthorize callback via the App Dashboard. Just go to your app, then choose the Settings menu, and finally the Advanced tab. A text field is provided for the Deauthorize Callback URL.
Whenever a user of your app de-authorizes it, this URL will be sent an HTTP POST containing a signed request. Read our guide to parsing the signed request to see how to decode this to find out the user ID that triggered the callback.
Additional Resources
Login Dialog
Facebook SDK for JavaScript Reference for FB.login()
Login Button
A simple way to trigger the Login Dialog.
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. Seeing herself thus transformed into so repulsive an object, Medusa fled from her home, never to return. Wandering about, abhorred, dreaded, and shunned by all the world, she now developed into a character, worthy of her outward appearance. In her despair she fled to Africa, where, as she passed restlessly from place to place, infant snakes dropped from her hair, and thus, according to the belief of the ancients, that country became the hotbed of these venomous reptiles. With the curse of Athene upon her, she turned into stone whomsoever she gazed upon, till at last, after a life of nameless misery, deliverance came to her in the shape of death, at the hands of Perseus
Athena was the Greek virgin goddess of reason, intelligent activity, arts and literature. She was the daughter of Zeus; her birth is unique in that she did not have a mother. Instead, she sprang full grown and clad in armour from Zeus' forehead.
She was fierce and brave in battle; however, she only took part in wars that defended the state and home from outside enemies. She was the patron of the city, handcraft, and agriculture. She invented the bridle, which permitted man to tame horses, the trumpet, the flute, the pot, the rake, the plow, the yoke, the ship, and the chariot. She was the embodiment of wisdom, reason, and purity. She was Zeus' favourite child and was allowed to use his weapons including his thunderbolt. Her holy tree was the olive tree and she was often symbolised as an owl..
She became the patron goddess of Athens after winning a contest against Poseidon by offering the olive tree to the Athenians. It is evident that Athena and Athens derive from the same root; Athens (or Athenae) is in plural form, because it represents the sisterhood of the goddess that existed there. Similarly, Athena was called Mykene in the city of Mycenae (also a plural after the respective sisterhood), and Thebe in the city of Thebes (or Thebae, both plural forms).
Athena Is also called Minerva, Athina, Athene.
See Also: Birth of Athena, Zeus, Poseidon, Theogony
