The console is displaying a null value outside of the block, however, the correct value is returned when

I am having an issue where the first console.log() is not returning the correct value, but the second one is. Can anyone provide assistance with this problem?

angular.module('resultsApp', ['ngCookies'])

    .config(['$qProvider', function ($qProvider) {
        $qProvider.errorOnUnhandledRejections(false);
    }])



      .controller('resultsController', function($scope) {
        var code = localStorage.getItem('code');
        $scope.data = "";

            var dataRef = firebase.database().ref("0/"+code);

            dataRef.on('value', function(snapshot){
                console.log(snapshot.val());
                $scope.data = snapshot.val();
            });
            console.log($scope.data)
      });
javascriptangularjsfirebasefirebase-realtime-database

Answer №1

In most cases, your code will be executed in the following order:

Exec 1--> $scope.data = "";

Exec 2--> var dataRef = firebase.database().ref("0/" + code);

Exec 3--> dataRef.on('value', function(snapshot) { //register event and wait for response asynchronously
Exec 5--> console.log(snapshot.val());
Exec 6--> $scope.data = snapshot.val();
});
Exec 4--> console.log($scope.data); //at this moment value of $scope.data = ""

To ensure that your code runs after getting the data, you can move it into a function called processData and then call it like this:

angular.module('resultsApp', ['ngCookies'])

.config(['$qProvider', function ($qProvider) {
    $qProvider.errorOnUnhandledRejections(false);
}])

.controller('resultsController', function($scope) {
    var code = localStorage.getItem('code');
    $scope.data = "";

        var dataRef = firebase.database().ref("0/" + code);

        dataRef.on('value', function(snapshot){
            console.log(snapshot.val());
            $scope.data = snapshot.val();
            console.log($scope.data);
            processData($scope); //call that function here
        });

});

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