如何让 return 等待 MySQL 连接结束？ Node.js

Question

我是新手 Node.js 我正在 Wix 上测试一些代码，以检查我的数据库是否在允许创建新帐户之前已经存在帐户名称（我故意不使用目前出于学习目的的 WHERE 标记）。

当前方法在连接完成之前检查帐户名称 returns，无法正确进行检查。

感谢任何帮助。

    export function tryToCreateAccount(login, password) 
{
    var mysql = require('mysql');

    var connection = mysql.createConnection({
        host: 'host',
        user: 'user',
        password: 'pass',
        database: 'db'
    });

    if(checkAccountName(login, connection))
    {
        console.log("Name didn't exist.");
    }
    else
    {
        console.log("Name Existed.");
    }
}

function checkAccountName(account_name, connection)
{
    var accountNameAvailable = true;

    connection.connect(function (err)
    {
        if(err) throw err;
        connection.query("SELECT login FROM accounts", function (err, result)
        {
            if (err) throw err;

            for(var i = 0; i < result.length ; i++)
            {
                if(result[i].login == account_name)
                {
                    console.log("Should of been false");
                    connection.end;
                    accountNameAvailable = false;
                }
            }

        });
        connection.end;
    });

    return accountNameAvailable;
}

Answer 1

欢迎来到 Node.js（以及异步函数（和 Promises（和回调））的世界）

我以“回调”的方式写了这篇文章，但我强烈建议您查看 async/await 以了解类似的内容，并了解“承诺”如何融入画面。

// to test, call tryToCreateAccount('login','pass',function(err,data){console.log(err,data)});

const mysql = require('mysql');
const connection = mysql.createConnection({
    host: 'host',
    user: 'user',
    password: 'pass',
    database: 'db'
});
export function tryToCreateAccount(login, password, next) 
{
    checkAccountName(login, connection, function(err, accountNameAvailable){
      if(err || !accountNameAvailable){
        console.log("Name didn't exist.");
        next(err || 'Name didn't exist.')
      }
      else
      {
        console.log("Name Existed.");
        next(null, true)
      }
   })
}

function checkAccountName(account_name, connection, next)
{
    var accountNameAvailable = false;

    connection.connect(function (err)
    {
        if(err) next(err);
        connection.query("SELECT login FROM accounts", function (err, result){
            if (err) next(err);
            for(var i = 0; i < result.length ; i++)
            {
                if(result[i].login == account_name)
                {
                    console.log("Should of been false");
                    connection.end;
                    accountNameAvailable = true;
                }
            }
            connection.end();
            next(null, accountNameAvailable);
        });

    });
}

Answer 2

我明白了为什么它什么也没做，因为连接结束而 next 在连接代码块中调用 next 为时已晚。

const mysql = require('mysql');
const connection = mysql.createConnection({
    host: 'host',
    user: 'user',
    password: 'pass',
    database: 'db'
});

export function tryToCreateAccount(login, password) 
{
    checkAccountName(login, connection, function(err, accountNameAvailable)
    {
      if(err || !accountNameAvailable){
        console.log("Name didn't exist.");
      }
      else
      {
        console.log("Name Existed.");
      }
   })
}

function checkAccountName(login, connection, next)
{
    var accountNameAvailable = false;

    connection.connect(function (err)
    {
        if(err) next(err);
        connection.query("SELECT login FROM accounts", function (err, result){
            if (err) next(err);
            for(var i = 0; i < result.length ; i++)
            {
                if(result[i].login == login)
                {
                    accountNameAvailable = true;
                }
            }
            next(null, accountNameAvailable);
            connection.end();
        });
    });
}

如何让 return 等待 MySQL 连接结束？ Node.js

How to make return wait for MySQL connection to end? Node.js

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