我正在使用 node.js 承诺验证数据库中是否存在用户名

Question

我想检查 mongo db 中是否存在用户名我想通过 promise 来做，我是 node.js 的新手，请帮助我了解实际情况提前谢谢。

var errorsArr = [];
var promise = username();
promise.then(function(data){
    errorsArr.push({"msg":"Username already been taken."});
},console.error);

username(function(err,data){
    User.findOne({"username":req.body.username},function(err,user) {
        if(err)
            return console.error(err);

        return user;
    });
});

console.log(errorsArr);

Answer 1

Mongoose 已经被承诺了，所以可以这样做：

function findUser() {
  return User.findOne({ "username": req.body.username })
    .then(function(user) {
      if (user) {
        // user exists, you can throw an error if you want
        throw new Error('User already exists!');
      }

      // user doesn't exist, all is good in your case
    }, function(err) {
      // handle mongoose errors here if needed


      // rethrow an error so the caller knows about it
      throw new Error('Some Mongoose error happened!');
      // or throw err; if you want the caller to know exactly what happened
    });
}

findUser().then(function() {
  // user doesn't exist, do your stuff

}).catch(function(err) {
  // here, you'll have Mongoose errors or 'User already exists!' error
  console.log(err.message);
});

Promise 是异步的，因此只返回 Promise，调用者将“等待”它解决并处理错误。