如何讓返回等待 MySQL 連接結束？ Node.js

Question

我是 Node.js 的新手，我正在 Wix 上測試一些代碼，以檢查我的數據庫在允許創建新帳戶之前是否已經存在帳戶名稱（我目前故意不使用 WHERE 標簽用於學習目的） .

目前，方法檢查帳戶名稱在連接完成之前返回，不允許正確進行檢查。

任何幫助表示贊賞。

    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

我弄清楚為什么它什么也沒做，因為連接結束，下一個調用太晚了，下一個在連接代碼塊內。

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();
        });
    });
}

Answer 2

歡迎來到 Node.js（以及異步函數（和承諾（和回調）的世界））

我已經以“回調”風格編寫了這個，但我強烈建議您研究 async/await 類似的東西，以及了解“承諾”如何融入圖片中。

// 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);
        });

    });
}