javascript - Is there something like angular $watch in node js -

i'm rookie in web services , knowledges not deep in node js, apologize in advance if question not correct. question have 2 functions in angular-node js app. first function, uploading file public folder on server

  var storage = multer.diskstorage({ //multers disk storage settings     destination: function (req, file, cb) {         cb(null, './demo/');     },     filename: function (req, file, cb) {         //var datetimestamp = date.now();         cb(null, file.originalname             //file.fieldname + '-' + datetimestamp + '.' + file.originalname.split('.')[file.originalname.split('.').length -1]         );     } }); var upload = multer({ //multer settings     storage: storage }).single('file'); /** api path upload files */ app.post('/upload', function(req, res) {     upload(req,res,function(err){         if(err){             res.json({error_code:1,err_desc:err});             return;         }         res.json({error_code:0,err_desc:null});     }); }); 

second funciton, calling executive java app

  var child = function() { spawn('java', ['-xms64m', '-xms64m', '-jar', '/home/ubuntu/code/parseexcel.jar',             '/var/www/html/demo/test.xls']);     child.on('close', function (exitcode) {         if (exitcode !== 0) {             console.error('something went wrong!');         }     });     child.stderr.on('data', function (data) {         process.stderr.write(data);     }); } 

is there angular $watch in node js set on file upload function, if file has been upload call java function

solution provided @paul (modified)

  app.post('/upload', function(req, res) {     upload(req,res,function(err){         if(err){             res.json({error_code:1,err_desc:err});             return;         }         // first, call child code:         var child = spawn('java', ['-xms64m', '-xms64m', '-jar', '/home/ubuntu/code/parseexcel.jar',             '/var/www/html/demo/test.xls']);         child.on('close', function (exitcode) {             if (exitcode !== 0) {                 console.error('something went wrong!');             }         });         child.stderr.on('data', function (data) {             process.stderr.write(data);         });         // in case java app parsing xls json around 5-8 sec, that's why i'm using timeout         settimeout(10000);         // respond client it's not waiting:         res.json({error_code:0,err_desc:null});     });     //return req.child; }); 

there're lot of ways organize code this, need call java function inside callback upload handler. should work:

 /** api path upload files */ app.post('/upload', function(req, res) {     upload(req,res,function(err){         if(err){             res.json({error_code:1,err_desc:err});             return;         }         // first, call child code:         child();         // respond client it's not waiting:         res.json({error_code:0,err_desc:null});     }); });