How to chain promise error functions in angularjs

Question

I know how to chain promises so that multiple success functions are executed. That is esplained in many examples. How do I chain promises so that multiple error functions are executed?

Answer 1

When an error is handled (and, either a value is returned or no value at all), the promise returned from then is considered resolved. You have to return a rejected promise from each error handler in order to propagate and chain error handlers.

For example:

promseA.then(
   function success() {
   },
   function error() {
      return $q.reject();
   })
.promiseB.then(
   function success() {
   },
   function error() {
      return $q.reject();
   })
.promiseC.then(
   function success() {
   },
   function error() {
      return $q.reject();
   });

Answer 2

then/fail function returns a promise, which can be rejected by throwing errors. If you want to chain multiple error handlers and trigger them all you should throw error from preceding error handlers.

var d = $q.defer();
d.promise.catch(errorHandler1).catch(errorHandler2);
d.reject();

function errorHandler1 {
 throw new Error();
}

function errorHandler2() {
  console.log("I am triggered");
}

Or instead of catch, you can use then method and pass errorHandler1 and errorHandler2 as a second parameter.