javascript - Angular's $q.reject() vs deferred.reject() -

i'm trying handle on angular $q service , related objects , apis. when @ objects in console see:

var deferred = $q.defer()  ...(and console inspection)...  $q: object {defer: function, reject: function, when: function, all: function}  deferred: object {resolve: function, reject: function, notify: function, promise: object}  deferred.promise: object {then: function, catch: function, finally: function} 

it raises few questions:

1. what's difference between $q.reject() , deferred.reject()? when use each?
2. what's relationship between errorfn in deferred.promise.then(successfn, errorfn) , catchfn in deferred.promise.catch(catchfn)?
3. if have bunch of nested promises , error occurs, outermost catch() function called? if 1 of nested promises has catch function defined? catch prevent outermost catch executing?

thanks.

1) $q.reject() shortcut create deferred , reject immediately; use in errorfn if can't handle error.

2) nothing, promise.catch(errorfn) syntactic sugar promise.then(null, errorfn), success , error methods of $http service, can write code following:

promise.     then(function(result){         // handle success         return result;     }, function errorhandler1(error){         // handle error, if separate catch in chain.      }).catch(function errorhandler2(error){         // handle errors errorhandler1     }); 

3) $q.reject can come in handy:

promise.     catch(function(error){        //decide can't handle error        return $q.reject(error); //this forwards error next error handler;     }).catch(function(error){        // here may handle error or reject again.        return 'an error occurred';         //now other errorfn in promise chain won't called,         // successfn calls will.     }).catch(function(error){        // never called because previous catch handles errors.     }).then(function(result){        //this called either result of promise if successful, or         //'an error occured' if wasn't     });