retry.js

function retry(retries, assertion, timeout, callbackSuccess, callbackFailure){
  var i = 0;
  function _retry() {
      i++;
      if (assertion) {
          callbackSuccess();
      } else {
          if (i < retries) {
              setTimeout(_retry, timeout);
          } else if (callbackFailure != undefined & i > retries) {
              callbackFailure();
          }
      }
  }
  _retry()
}



var assertion = function(){FB.length > 0}
var callbackFailure = function(){displayError(".fb-messages-box", "An error occurred", "Could not set up Facebook SDK.");}
retry(4, assertion, 500, get_fb_pages, callbackFailure)