yuan.promise

• create an Promise instance

  // ES6 required.
  
  function _promise_http_get(url) {
     var callbacks = {};
  
     // Do something async.
     http
         .get(url, function(res) {
             callbacks.onsuccess(res);
         })
         .on('error', function(ex) {
             callbacks.onerror(ex);
         })
         ;
  
     return yuan.promise(callbacks);
  };
  
  var res = yield _promise_http_get(url);