Why are my Facebook access tokens expring in Javascript - facebook

Question

I am creating a website using Parse, and I have run into an issue. When I let my browser sit around for a couple hours, calls to the graph API don't seem to work anymore. The response from the graph api is:
Error validating access token: Session has expired on Wednesday,
29-Apr-15 00:00:00 PDT. The current time is Wednesday, 29-Apr-15
21:34:32 PDT.
Of course, my token has expired... but now I can't find a way to easily refresh my access token without sending the user back through the login process... which isn't an ideal workflow.
A glimmer of hope in the Facebook Javascript documentation has me wondering if I am potentially just doing something wrong. If not, their documentation is horribly misleading.
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.
source: https://developers.facebook.com/docs/facebook-login/login-flow-for-web/v2.3#token
What can we do to automatically refresh this token?

Answer 1

The JS SDK should automatically provide fresh access tokens, yes – although I am not sure if it does so if you just have the app open for a couple of hours without interacting with it (meaning: reloading the page, so that the JS SDK gets re-initialized as well). Since this is not a very common use case, it might not.
I would suggest that you try and use FB.getLoginStatus to get a fresh access token. (There should be no need to then set this access token explicitly on subsequent API calls; that the SDK will handle itself.)
This method uses an internally cached result, to avoid having to make a request to Facebook every time it is called. Since the expiry time of a token is known, I would expect the SDK to be able to decide itself if an actual request is necessary again – but if it doesn’t, you can also force a new request by setting the second parameter to true. (This is however not recommendable for every call, so I would try and see if calling the method without it is able to resolve the problem already.)

Answer 2

A simple workaround is to make an API call before the current access_token expired.
Let's say the token expires every 2 hours, you can, for example, make a simple /me call every 1H30 :
/**
* Make an API Call to refresh the access_token
*/
function tokenRefresh() {
FB.api("/me", function (response) {
// the token is refreshed
});
}
// call it every 1H30
var tokenTimeout = window.setTimeout(tokenRefresh, 5400000);
If you don't want that code be executed when your user uses the app, so when it will be useless, you can, each time you make a request, reset the timeout in the callback :
window.clearTimeout(tokenTimeout);
var tokenTimeout = window.setTimeout(tokenRefresh, 5400000);
Therefore, your app makes a call each 1H30 that passed without an API call.