javascript - Promise code are read twice -

i use following code read json file , return promise i've 2 questions

return globasync("folder/*.json").catch(function (err) {     throw new error("error read: " + err); }).map(function (file) {     return fs.readfileasync(file, 'utf8')         .then(function (res) {             console.log("test");             return json.parse(res);          },         function (err) {             throw new error("error :" + err);         }).then(function () {             console.log("test2");         }); }); 

i use console log , see console printed twice

test test test2 test2 

why happening , how avoid ?

2. in place i've put console.log("test2"); need invoke event json parse finished , still return outside json object (to caller), when add last then doesn't work(the returned object undefined),any idea how right?

update try following doesn't work...

return globasync("folder/*.json").catch(function (err) {             throw new error("error read: " + err);         }).map(function (file) {             return fs.readfileasync(file, 'utf8')                 .then(function (res) {                     console.log("test");                     json.parse(res); //data parse                 }.catch(function (err) {                         throw new error("error :" + err);                     }                 ).then(function (data) {                         obj.emit('ready');                         return data;                     }))         });     } 

update2 able solve add new return json.parse(res); how should solve first issue method called twice

like @jaromandax said, got 2 *.json files. try print out file name instead , should become more obvious. in case, .map expected called twice, once each file. otherwise aren't gonna able read , parse 2 files together.

if want converge single point after file reads , parses complete, need chain .then after .map. eg.

return globasync("folder/*.json")     .map(function(file) {         ...     })     .then(function() {         obj.emit('ready');     }); 

edit answer question in comment. there few things should keep in mind.

1. throwing error inside promise chain caught promise , send rejection flow. may still throw error if interested in getting custom error type or printing stack trace in desirable way. people prefer return promise.reject(error).
2. any rejection in .map send promise chain rejection flow.
3. inside rejection chain, if want continue down rejection flow. need return promise.reject(error), otherwise if don't return reject object, can bring resolve flow.

if want want handle each error individually, can this:

return globasync("folder/*.json")     .catch(function(error) {         // todo: handle error         return promise.reject(error);     })     .map(function(file) {         return fs.readfileasync(file, 'utf8')             .catch(function(error) {                 // todo: handle error                 return promise.reject(error);             })             .then(function(res) {                 return json.parse(res);             });     })     .then(function() {         obj.emit('ready');     }); 

if want handle once glob , once file read, have bit more creative.

return globasync("folder/*.json")     .catch(function(error) {         // todo: handle error         return promise.reject(error);     })     .then(function(files) {         return promise.resolve(files)             .map(function(file) {                 return fs.readfileasync(file, 'utf8');             })             .catch(function(error) {                 // todo: handle error once read error                 return promise.reject(error);             })             .map(function(res) {                 // judging original code, not handling                 // parser error, wrote code behave equivalent                 // original. otherwise chain parse immediate after                 // readfileasync.                 return json.parse(res);             });     })     .then(function() {         obj.emit('ready');     });