javascript可观察的错误处理

Question

I am trying to generate custom error handling when my observable fails instead of getting a big 404 error in my console. However, no matter how many tutorials I read I jsut can't figure out how it works.

my code is as follows:

datacontext.graph.getUserProfilePicture('', detailedData.id)
.then(function success(photo) {
    console.log("succesful call" + photo);
})
.catch(function error(err) {
    console.log("error" + err);
});

The success statement works, however the fail method doesn't.

Here is the call that I make to the ,icrosoft graph endpoint:

function getUserPic(principalName) {
            var deferred = $q.defer();
            var endpoint = config.baseGraphApiUrl + "users/" + principalName + "/photo/$value";
            $http.get(endpoint, { responseType: 'blob' }).then(function (result) {
                var file = new Blob([result.data], { type: 'image/jpeg' });
                var fileURL = URL.createObjectURL(file);

                deferred.resolve(fileURL);
            }, function (data) {
                console.log(error);
            });

            return deferred.promise;
        }

on success it returns: succesful call blob: http://localhost:8480/7da29a36-d13d-440f-8207-75f1cde58fcf

on failure it returns: https://graph.microsoft.com/v1.0/users/63c31121-cd15-4f48-ba43-8dea613f19cd/photo/ $value 404 (Not Found)

Answer 1

Have you tried this:

.then(function success(photo) {
    console.log("succesful call" + photo);
}, function(err){
    console.log("error" + err);
})

?

Answer 2

The success statement works, however the fail method doesn't.

.getUserProfilePicture returns a promise. A promise either succeeds (resolved) or fails (rejected). If getUserProfilePicture resolves even by passing invalid data then it has bugs. Your posted code has no problem regarding handling promises' different states.

If you want to reject the promise manually you can throw an error in your success handler:

datacontext.graph.getUserProfilePicture('', detailedData.id)
.then(function success(photo) {
    console.log("succesful call" + photo);
    throw new Error('I am an error!');
})
.catch(function error(err) {
    console.log("error" + err);
});