Nodejs Async use Method (solve multi-layer callback nesting)

Since Nodejs is processed asynchronously, sometimes we want to synchronize the data out of MySQL, and finally we need to use this extension in processing logic;

This extension avoids multiple levels of callbacks;

Installation method:

NPM Install Async

How to use: 1, parallel multiple functions in parallel execution 

1 varAsync = require (' async ');2 3 Async.Parallel (4     [5         function(callback) {6             //Query Database code here7Daouser.getuserbyid (UserId,function(err, user) {8 callback (err, user);9             });Ten         }, One         function(callback) { A             //Query Database code here -Daouser.gettotal (Callback,function(Err, count) { - callback (Err, count); the             }); -         } -         //If you still need to query the data to continue adding methods -     ], +     function(err, results) { -         varuser = Results[0]; +         varCount = results[1]; A     } at);

2, waterfall several methods to execute sequentially, the return value of the previous function can be passed to the next function

1 varAsync = require (' async ');2 3 Async.waterfall ([4     function(callback) {5Daouser.getuseridbyname (UName,function(Err, userId) {6CallbackNULL, userId);7         });8     },9     function(UserId, callback) {TenDaotask.getdatebyuid (UserId,function(err, tasks) { OneCallbackNULL, tasks); A         }); -     } -],function(err, result) { the     vartasks =result; -});

Nodejs Async use Method (solve multi-layer callback nesting)