Angular HttpPromise difference between success error methods and then s arguments

Question

According to AngularJS doc  calls to  http return the following      Returns a promise object with the standard then method and two http specific methods  success and error  The then method takes two arguments a success and an error callback which will be called with a response object  The success and error methods take a single argument - a function that will be called when the request succeeds or fails respectively  The arguments passed into these functions are destructured representation of the response object passed into the then method    Aside from the fact that the response object is destructured in one case  I don t get the difference between   the success error callbacks passed to be passed as arguments of promise then the callbacks passed as arguments for the promise success promise error methods of the promise   Is there any  What s the point of these two different ways to pass seemingly identical callbacks

User · Answer

Just for completion  here is a code example indicating the differences   success   error    http get   someURL    success function data  status  header  config           success handler     error function data  status  header  config           error handler       then    http get   someURL    then function response           success handler    function response           error handler     then function response           success handler    function response           error handler     then function response           success handler    function response           error handler

User · Answer

There are some good answers here already   But it s worthwhile to drive home the difference in parallelism offered    success   returns the original promise then   returns a new promise   The difference is then   drives sequential operations  since each call returns a new promise    http get             then function seqFunc1 response               then function seqFunc2 response                http get   seqFunc1   seqFunc2     success   drives parallel operations  since handlers are chained on the same promise    http             success function parFunc1 data               success function parFunc2 data                http get   parFunc1    parFunc2   in parallel

User · Answer

then   is chainable and will wait for previous  then   to resolve    success   and  error   can be chained  but they will all fire at once  so not much point to that    success   and  error   are just nice for simple calls  easy makers     http post   getUser   success function user                 so you don t have to type this    http post  getUser   then function response     var user   response data       But generally i handler all errors with  catch      http get           then function response             successHandler          do some stuff       return  http get   somethingelse      get more data             then anotherSuccessHandler       catch errorHandler    If you need to support  lt   IE8 then write your  catch   and  finally   like this  reserved methods in IE         then successHandler        catch   errorHandler    Working Examples    Here s something I wrote in more codey format to refresh my memory on how it all plays out with handling errors etc   http   jsfiddle net nalberg v95tekz2

User · Answer

Official Notice  success and error have been deprecated  please use the standard then method instead      Deprecation Notice             The  http legacy promise methods success and error have been deprecated  Use the standard then method instead  If    httpProvider useLegacyPromiseExtensions is set to false then these   methods will throw  http legacy error    link  https   code angularjs org 1 5 7 docs api ng service  http  screenshot  view the screenshot

User · Answer

Some code examples for simple GET request  Maybe this helps understanding the difference  Using then    http get   someURL   then function response        var data   response data          status   response status          header   response header          config   response config         success handler    function response        var data   response data          status   response status          header   response header          config   response config         error handler       Using success error    http get   someURL   success function data  status  header  config           success handler    error function data  status  header  config           error handler

User · Answer

NB This answer is factually incorrect  as pointed out by a comment below  success   does return the original promise   I ll not change  and leave it to OP to edit     The major difference between the 2 is that  then   call returns a promise  resolved with a value returned from a callback  while  success   is more traditional way of registering callbacks and doesn t return a promise   Promise-based callbacks   then    make it easy to chain promises  do a call  interpret results and then do another call  interpret results  do yet another call etc     The  success   method is a streamlined  convenience method when you don t need to chain call nor work with the promise API  for example  in routing    In short     then   - full power of the promise API but slightly more verbose  success   - doesn t return a promise but offeres slightly more convienient syntax

[angularjs] Angular HttpPromise: difference between `success`/`error` methods and `then`'s arguments

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