Question

I build a Firefox Extension and i’m using the graph api. At the moment i catch the access token of each user while starting the browser like:
https://stackoverflow.com/questions/10301146/facebook-login-within-a-firefox-add-on

This works fine but kind of stupid, because nobody will use the extension in each firefox session. So what i’m trying to do is, catch the access token or more accurately call the methode Wladimir Palant recommends on demand. My code looks like this, while getAccessToken() is the mentioned method.

onLoad: function (){
   var NoteHandler = window.arguments[0];
   var sjcl = NoteHandler.sjcl;
   NoteHandler.getAccessToken();
   decryptionDialog.noteHandler = NoteHandler;
   decryptionDialog.sjcl = sjcl;

   var currID = decryptionDialog.getID();

   if(currID==""){
      window.close();
      return false;
     }else{             
       http_request = new XMLHttpRequest();   
       http_request.open('Get', 'https://graph.facebook.com/'+currID+'/notes?access_token='+NoteHandler.token, false);
       http_request.overrideMimeType("text/json");
       http_request.send(null);

       decryptionDialog.value = decryptionDialog.ResponseToArray(http_request.responseText);
....

But the problem is while getAccessToken() is still waiting for the access token, the onLoad()-Method won’t wait and goes on. Therefore the NoteHandler.token is null while the request is send. Does anyone have an idea, because i’m relatively new to javascript.

Answer 1

You should rewrite this code to be asynchronous – it shouldn’t assume that getAccessToken() will get the result immediately, there should be rather a callback parameter, a function to be called when the operation is done (can be a closure function). Something along these lines:

onLoad: function (){
   var NoteHandler = window.arguments[0];
   var sjcl = NoteHandler.sjcl;
   NoteHandler.getAccessToken(function()
   {
       decryptionDialog.noteHandler = NoteHandler;
       decryptionDialog.sjcl = sjcl;

       ...

       http_request.open('Get', 'https://graph.facebook.com/'+currID+'/notes?access_token='+NoteHandler.token, false);

       ...
   });
}

...

getAccessToken: function(callback) {
    ...

    // All done - call the callback
    callback();
}