问题描述
这是我使用 Node.js 和 sqlite3 的第一个项目。由于节点是异步的,我真的很挣扎,因为我有一个 .js 文件专门用于与我的数据库交互的函数。但这意味着,每当我尝试调用这些函数并将它们分配给变量时,我尝试对变量执行的操作都会在我分配之前运行。例如:
//From my .js file that handles server stuff
app.post('/login',function (req,res,next) {
placeholder = loginVer("Test","Test")
console.log(placeholder) //Outputs pending promise
})
//From my database.js file
function databaseUserQuery(email){
return new Promise(function (resolve,reject) {
info = [] //empty array,if query can't find anything,info stays null which serves the purpose
db.each("SELECT Email emailS,Password pword FROM Users WHERE Email = ?",[email],(err,row) => {
info[0] = row.emailS;
info[1] = row.pword;
resolve(info);
})
setTimeout(() => {
resolve(info);
},10)
})
}
async function loginVer(email,password) {
await databaseUserQuery(email).then(function(result) {
if(result[0] == email){ //Checks if user exists (via email)
if(result[1] == password){return(0)} //returns 0 if password matches
else{return(1)} //Returns 1 if password is wrong but user exists
} else {return(2)} //Returns 2 if user does not exist
})
}
如果代码本身不好,我很抱歉,但我已经使用 promise 来确保在调用 loginVer 函数时,它首先执行查询,然后继续处理输出,但我真的认为/希望有更好的方法来做到这一点。
解决方法
非常简单,您只需使用.then
!
app.post('/login',function (req,res,next) {
loginVer("Test","Test").then(placeholder => {
// hey the promise is resolved now and we got data!
console.log(placeholder);
res.send(placeholder);
})
})
此外,您没有正确返回数据。
function loginVer(email,password) {
return new Promise(resolve => {
await databaseUserQuery(email).then(function(result) {
if (result[0] == email) { //Checks if user exists (via email)
if (result[1] == password) {
resolve(0)
return;
} //returns 0 if password matches
else {
rresolve(1)
} //Returns 1 if password is wrong but user exists
} else {
resolve(2)
} //Returns 2 if user does not exist
})
});
}
另外,我建议您查看 bcrypt。您似乎将密码存储在您的数据库中,这是一个巨大的安全风险!使用 bcrypt 散列密码,这样如果有人进入您的数据库,您就不会泄露密码!
,//changed handler to async function
app.post('/login',async function (req,next) {
try {
//you can use await here now
let placeholder = await loginVer("Test","Test")
console.log(placeholder) //Outputs pending promise
} catch (error) {
//any error with throw or reject statement in underlying function calls will propagate here
console.log(error)
}
})
//From my database.js file
function databaseUserQuery(email) {
return new Promise(function (resolve,reject) {
info = [] //empty array,if query can't find anything,info stays null which serves the purpose
db.each("SELECT Email emailS,Password pword FROM Users WHERE Email = ?",[email],(err,row) => {
if (err) {
return reject(err)
}
info[0] = row.emailS;
info[1] = row.pword;
resolve(info);
})
})
}
async function loginVer(email,password) {
//either user async await or use promise chaining. databaseUserQuery returns promise so we can use await here
let result = await databaseUserQuery(email)
if (result[0] == email) { //Checks if user exists (via email)
if (result[1] == password) { return (0) } //returns 0 if password matches
else { return (1) } //Returns 1 if password is wrong but user exists
} else { return (2) } //Returns 2 if user does not exist
}
-
async/await
和then/catch
可互换。 - 如果一个函数返回一个 promise,您可以使用
async/await
方式或then/catch
方式。await databaseUserQuery(email).then(function(result) {
在此语句中,您将两者混合使用。 - 总是用
try/catch
或.catch
捕捉错误。所以调试问题会更容易。