javascript - code inside ref once not executing angularjs -

code inside this.verifyusertoken block of not execute. guess has asynchronous calls being data returned not ready seem not know how go it.

this.verifyusertoken = function(){             //check if token matches existing token , if verified true             ref.orderbychild('token').equalto(this.token).once('value').             then(function(datasnapshot){                 //if token matches                     if(datasnapshot.val()){                         alert("token exists",datasnapshot.val().token);                         $scope.isverified = "yes";                     }else{                         alert("token not exist",datasnapshot.val());                         $scope.isverified = "no";                     }             });         }  this.registeruser = function(){             console.log("entered registeruser()");              this.verifyusertoken();             alert("the value of isverified:"+ $scope.isverified);             if($scope.isverified == "yes"){                     alert("verifying user token...",this.verifyusertoken());                     $scope.auth.$createuser({                     "email": this.email,                     "password" : this.password                 }).then(function(userdata){                     alert("successfully created user account uid:", userdata.uid);                     //redirect /userlogin if registration successful                     //this.changeverifiedstatus();                     alert("user verifed , changed");                     $location.path('/userlogin');                 }).catch(function(error){                     alert("error creating user:",error);                 });             }else{                 alert("token failed verification");             }                }; 

since verifyusertoken has assync call firebase can handle returning promise function , proceed registeruser after having ther verify call finished.

i've set jsfiddle can see working.

this.verifyusertoken = function(){   //check if token matches existing token , if verified true   var verifyusertokenpromise = new promise(function(resolve, reject){                                                    ref.orderbychild('token').equalto(this.token).once('value').then(function(datasnapshot){       //if token matches           if(datasnapshot.val()){               alert("token exists",datasnapshot.val().token);               $scope.isverified = "yes";           }else{               alert("token not exist",datasnapshot.val());               $scope.isverified = "no";           }           //resolve promise. can pass data here           resolve($scope.isverified);     });   });   return verifyusertokenpromise; };  this.registeruser = function(){   console.log("entered registeruser()");    this.verifyusertoken().then(function(result){     alert("the value of isverified:"+ $scope.isverified);     if($scope.isverified == "yes"){             alert("verifying user token...",this.verifyusertoken());             $scope.auth.$createuser({             "email": this.email,             "password" : this.password         }).then(function(userdata){             alert("successfully created user account uid:", userdata.uid);             //redirect /userlogin if registration successful             //this.changeverifiedstatus();             alert("user verifed , changed");             $location.path('/userlogin');         }).catch(function(error){             alert("error creating user:",error);         });     }else{         alert("token failed verification");     }      }) };