一段 node.js 代码，如何优化防止 callback hell？

This topic created in 3598 days ago, the information mentioned may be changed or developed.

users.userExists({
        username: username
      }, function(err, exists) {
        if (err) {
          users.close();
          console.error('Error testing if user exists: ' + err);
          response.error = '业务忙，请稍候重试';
          res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);
          return;
        } else if (exists) {
          users.close();
          response.error = '用户名已经存在';
          res.status(HttpStatus.CONFLICT).json(response);
          return;
        } else {
          users.emailExists(profile.email, function(err, exists) {
            console.log(profile.email +' ' + exists);
            if (err) {
              users.close();
              console.error('checking email error');
              response.error = '业务忙，请稍候重试';
              res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);
              return;
            } else if (exists) {
              users.close();
              response.error = '邮箱 ' + profile.email + ' 已存在';
              res.status(HttpStatus.CONFLICT).json(response);
              return;
            }
            users.createUser(username, password, profile, function(err, uid, hash) {
              if (err) {
                response.error = '生成用户错误';
                console.error('Failed to create user ' + err);
                res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);
              } else {
                response.statusMessage = '成功生成用户';
                response.uid = uid;
                // best-effort without a callback
                res.json(response);

              }
            });
          });
        }
      })

err

response

exists

JSON

12 replies • 2016-07-23 07:40:24 +08:00

zwh8800

Jul 22, 2016

用 async ＋ await

zealic

Jul 22, 2016

你都知道 callback hell 了，为什么不知道 Promise

shiny

PRO

Jul 22, 2016

Promise 模式，还可以加点 ES2015 语法糖会更甜。

zenxds

Jul 22, 2016

https://github.com/tj/co

Mirachael

Jul 22, 2016

挖坟贴？

plqws

Jul 22, 2016

这种程度的 hell 还好啦
按照楼主这样子的代码， async await 可能还得配合 tuple 使用…

zhuangzhuang1988

Jul 22, 2016

如果闲的蛋疼的话可以试试 http://fsprojects.github.io/Fable/
最后结果类似这样
```F#
async {
try
let! exists = users.userExists({username: username})
if exists:
res.status(HttpStatus.CONFLICT).json(response);
return;
try:
let! users.emailExists(profile.email)
if exists:
response.error = '邮箱 ' + profile.email + ' 已存在';
res.status(HttpStatus.CONFLICT).json(response);
return
try:
let! (uid, hash) = users.createUser(username, password, profile)
response.statusMessage = '成功生成用户';
response.uid = uid;
res.json(response);
except err:
response.error = '生成用户错误';
console.error('Failed to create user ' + err);
res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);

except err:
console.error('checking email error');
response.error = '业务忙，请稍候重试';
res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);
except err:
console.error('Error testing if user exists: ' + err);
response.error = '业务忙，请稍候重试'
res.status(HttpStatus.INTERNAL_SERVER_ERROR).json(response);
finally:
users.close()
}

```

zhuangzhuang1988

Jul 22, 2016

擦 , 空格都没了