如何在 node.js 中使用 Promise 和 express？
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how to use Promise with express in node.js?
提问by hu7sy
I am using Promise with Express.
我在 Express 中使用 Promise。
router.post('/Registration', function(req, res) {
var Promise = require('promise');
var errorsArr = [];
function username() {
console.log("1");
return new Promise(function(resolve, reject) {
User.findOne({ username: req.body.username }, function(err, user) {
if(err) {
reject(err)
} else {
console.log("2");
errorsArr.push({ msg: "Username already been taken." });
resolve(errorsArr);
}
});
});
}
var username = username();
console.log(errorsArr);
});
When I log errorsArray, it is empty and I don't know why. I am new in node.js. Thanks in advance.
当我登录时errorsArray，它是空的，我不知道为什么。我是 node.js 的新手。提前致谢。
采纳答案by anolsi
Try the following, and after please read the following document https://www.promisejs.org/to understand how the promises work.
尝试以下操作，然后请阅读以下文档https://www.promisejs.org/以了解 Promise 的工作原理。
var Promise = require('promise');
router.post('/Registration',function(req,res,next) {
function username() {
console.log("agyaaa");
return new Promise(function(resolve,reject) {
User.findOne({"username":req.body.username}, function(err,user) {
if (err) {
reject(err)
} else {
console.log("yaha b agyaaa");
var errorsArr = [];
errorsArr.push({"msg":"Username already been taken."});
resolve(errorsArr);
}
});
});
}
username().then(function(data) {
console.log(data);
next();
});
});
You can have other errors also (or things that shouldn't be done that way). I'm only showing you the basic use of a Promise.
您也可能有其他错误（或不应该那样做的事情）。我只是向您展示了 Promise 的基本用法。
回答by Gokul Thulaseedharan
router.post('/Registration', function(req, res) {
return User
.findOne({ username: req.body.username })
.then((user) => {
if (user) {
return console.log({ msg:"Username already been taken" });
}
return console.log({ msg: "Username available." });
})
.catch((err)=>{
return console.error(err);
});
});
you can write a clean code like this. Promise is a global variable available you don't need to require it.
你可以像这样写一个干净的代码。Promise 是一个可用的全局变量，您不需要它。
