javascript - AngularJs : Callback or promise in a service using conditions -

i have specific case i'm not sure if should implement callback or promise. i'm totally new promises , starting understand concept. therefor i'd not fall anti patterns.

i did read , re-read angular doc $q.

so implement :

if using promises :

oauthservice.token().then(function(access_token){     config.url = config.url+'?access_token='+access_token; });  return config; 

if using callback :

oauthservice.token(function(access_token){     config.url = config.url+'?access_token='+access_token; });  return config; 

oauth service not http request if has conditions in let me think should use callback instead of promises.

so here service using callback now.

oauthservice.js :

app.factory('oauthservice', function($http, $localstorage) {  return {     token : function(callback){          // actual token         access_token = $localstorage.getobject('access_token');         // actual identity         identity_token = $localstorage.getobject('identity_token');          // if no user logged         if(isobjectempty(identity_token)){              // if access_token not exist or expires             if( isobjectempty(access_token) || date.now() > (access_token.expires_at - (600*1000)) ){                  // create anonymous access_token                 $http                     .get(domain+'/oauth/v2/token?client_id='+public_id+'&client_secret='+secret+'&grant_type=client_credentials')                     .then(function (response) {                          $localstorage.setobject('access_token', {                             key: response.data.access_token,                             type: 'anonymous',                             expires_at: date.now()+(response.data.expires_in*1000)                         });                          // return access token here                         callback(response.data.access_token);                      });             }          }         // if user logged         else{              // if access_token not exist or expires or anonymous             if( isobjectempty(access_token) || date.now() > (access_token.expires_at - (600*1000)) || access_token.type == 'anonymous' ){                 // create access_token identity                 $http                     .get(domain+'/oauth/v2/token?client_id='+public_id+'&client_secret='+secret+'&api_key='+identity_token+'&grant_type=http://oauth2.dev/grants/api_key')                     .then(function (response) {                          $localstorage.setobject('access_token', {                             key: response.data.access_token,                             type: 'identity',                             expires_at: date.now()+(response.data.expires_in*1000)                         });                          // return access token here                         callback(response.data.access_token);                      });             }          }          // return access token here (if previous token has not changed of type or expired)         callback(access_token.key);      } };  }) 

so if i'd rather go promises how should implement that?

having conditions in operation has nothing callbacks vs. promises. plain callbacks crappy way asynchronous operations , should use promises whenever can.

you can rewrite token method use promises this:

app.factory('oauthservice', function($http, $localstorage, $q) {     return {         token : function(callback){              // actual token             access_token = $localstorage.getobject('access_token');             // actual identity             identity_token = $localstorage.getobject('identity_token');              // if no user logged             if(isobjectempty(identity_token)){                  // if access_token not exist or expires                 if( isobjectempty(access_token) ||                      date.now() > (access_token.expires_at - (600*1000)) ){                      // create anonymous access_token                     return $http                         .get(domain+'/oauth/v2/token?client_id='+public_id +                               '&client_secret=' + secret + '&grant_type=client_credentials')                         .then(function (response) {                             $localstorage.setobject('access_token', {                                 key: response.data.access_token,                                 type: 'anonymous',                                 expires_at: date.now() +                                         (response.data.expires_in * 1000)                             });                              return response.data.access_token;                         });                 }             }              // if user logged             else {                 // if access_token not exist or expire or anonymous                 if( isobjectempty(access_token) ||                      date.now() > (access_token.expires_at - (600*1000)) ||                      access_token.type == 'anonymous' ){                      // create access_token identity                     return $http                         .get(domain+'/oauth/v2/token?client_id='+public_id+'&client_secret='+secret +                               '&api_key='+identity_token+'&grant_type=http://oauth2.dev/grants/api_key')                         .then(function (response) {                             $localstorage.setobject('access_token', {                                 key: response.data.access_token,                                 type: 'identity',                                 expires_at: date.now()+                                       (response.data.expires_in * 1000)                             });                              return response.data.access_token;                             });                 }              }              // return access token here (if previous token has not changed of type or expired)             return $q.when(access_token.key);             }     }; }); 

and can bit of refactoring reduce this:

app.factory('oauthservice', function($http, $localstorage, $q) {     function expiressoon(access_token) {         return date.now() > (access_token.expires_at - (600*1000));     }      function getaccesstoken(url, type) {         return $http             .get(url)             .then(function (response) {                 $localstorage.setobject('access_token', {                     key: response.data.access_token,                     type: type,                     expires_at: date.now() +                          (response.data.expires_in * 1000)             });                  return response.data.access_token;             });     }      return {         token : function(callback){              // actual token             access_token = $localstorage.getobject('access_token');             // actual identity             identity_token = $localstorage.getobject('identity_token');              // if no user logged             if(isobjectempty(identity_token)){                  // if access_token not exist or expires                 if( isobjectempty(access_token) || expiressoon(access_token) ) {                     var url = domain + '/oauth/v2/token?client_id=' + public_id +                                '&client_secret=' + secret + '&grant_type=client_credentials';                     // create anonymous access_token                     return getaccesstoken(url, 'anonymous');                 }             }              // if user logged             else {                 // if access_token not exist or expire or anonymous                 if( isobjectempty(access_token) ||                      expiressoon(access_token) ||                      access_token.type == 'anonymous' ){                      var url = domain+'/oauth/v2/token?client_id=' + public_id+                               '&client_secret='+secret +                                '&api_key='+identity_token +                                '&grant_type=http://oauth2.dev/grants/api_key';                      // create access_token identity                     return getaccesstoken(url, 'identity');                 }             }              // return access token here (if previous token has not changed of type or expired)             return $q.when(access_token.key);             }     }; });