节点找不到已安装的mysql模块

Question

我正在尝试使用node-mysql模块连接到我的数据库。 一切正常，我更新了我的脚本（甚至连连接脚本都没有），突然间它找不到mysql模块。

这是我的连接脚本db_connect：

var mysql      = require('mysql');
var connection = mysql.createConnection({
    host     : 'localhost',
    user     : 'root',
    password : '',
    database : 'officeball'
});

作为参考，这是我更改的两个脚本，login.js：

console.log('login module initialized');

var express     = require('express');
var app         = express();
var validator   = require('./validator');

var username;
var password;

function listen(){
    app.use(express.bodyParser());

    app.post('/login', function(req, res) {
        console.log('User ' + req.body.email + ' is attempting login...');
        username = req.body.email;
        password = req.body.password;
        validator.validate(username,password);  
        if (validator.validate() === req.body.email){
            res.writeHead(302, {'Location': 'http://localhost/officeball/app.php'});
        }
        res.end();
    });

    app.listen(8080, function() {
        console.log('Server running at http://127.0.0.1:8080/');
    });
}

exports.listen = listen;

和主要的变化，validator.js：

console.log('validator module initialized');
var login = require("./db_connect");

function validate(username, password, callback){

    connection.connect(function (err){
        console.log('Connection with the officeball MySQL database openned...');
        if (err) return callback(new Error('Failed to connect'), null);
        // if no error, you can do things now.

        connection.query('select username,password from users where username=?',
                username,
                function(err,rows,fields) {
                    //  we are done with the connection at this point), so can close it
                    connection.end();
                    console.log('...Connection with the officeball MySQL database closed.');

                    // here is where you process results
                    if (err)
                        return callback(new Error ('Error while performing query'), null);
                    if (rows.length !== 1)
                        return callback(new Error ('Failed to find exactly one user'), null);

                    // test the password you provided against the one in the DB.
                    // note this is terrible practice - you should not store in the
                    // passwords in the clear, obviously. You should store a hash,
                    // but this is trying to get you on the right general path

                    if (rows[0].password === password) {
                        // you would probably want a more useful callback result than 
                        // just returning the username, but again - an example
                        return callback(null, rows[0].username);
                    } else {
                        return callback(new Error ('Bad Password'), null);
                    }

                });


    });
};

exports.validate = validate;

控制台日志：

C:\xampp\htdocs\officeball\node_scripts>npm install node-mysql
npm http GET https://registry.npmjs.org/node-mysql
npm http 200 https://registry.npmjs.org/node-mysql
npm http GET https://registry.npmjs.org/node-mysql/-/node-mysql-0.3.7.tgz
npm http 200 https://registry.npmjs.org/node-mysql/-/node-mysql-0.3.7.tgz
npm http GET https://registry.npmjs.org/cps
npm http GET https://registry.npmjs.org/better-js-class
npm http GET https://registry.npmjs.org/underscore
npm http GET https://registry.npmjs.org/mysql
npm http 200 https://registry.npmjs.org/better-js-class
npm http GET https://registry.npmjs.org/better-js-class/-/better-js-class-0.1.3.
tgz
npm http 200 https://registry.npmjs.org/underscore
npm http GET https://registry.npmjs.org/underscore/-/underscore-1.6.0.tgz
npm http 200 https://registry.npmjs.org/cps
npm http GET https://registry.npmjs.org/cps/-/cps-1.0.0.tgz
npm http 200 https://registry.npmjs.org/better-js-class/-/better-js-class-0.1.3.
tgz
npm http 200 https://registry.npmjs.org/mysql
npm http 200 https://registry.npmjs.org/underscore/-/underscore-1.6.0.tgz
npm http 200 https://registry.npmjs.org/cps/-/cps-1.0.0.tgz
npm http GET https://registry.npmjs.org/require-all/0.0.3
npm http GET https://registry.npmjs.org/readable-stream
npm http GET https://registry.npmjs.org/bignumber.js/1.0.1
npm http 304 https://registry.npmjs.org/require-all/0.0.3
npm http 304 https://registry.npmjs.org/readable-stream
npm http 200 https://registry.npmjs.org/bignumber.js/1.0.1
npm http GET https://registry.npmjs.org/bignumber.js/-/bignumber.js-1.0.1.tgz
npm http 200 https://registry.npmjs.org/bignumber.js/-/bignumber.js-1.0.1.tgz
npm http GET https://registry.npmjs.org/debuglog/0.0.2
npm http GET https://registry.npmjs.org/core-util-is
npm http GET https://registry.npmjs.org/string_decoder
npm http 304 https://registry.npmjs.org/core-util-is
npm http 304 https://registry.npmjs.org/string_decoder
npm http 304 https://registry.npmjs.org/debuglog/0.0.2
node-mysql@0.3.7 node_modules\node-mysql
├── better-js-class@0.1.3
├── cps@1.0.0
├── underscore@1.6.0
└── mysql@2.1.0 (require-all@0.0.3, readable-stream@1.1.11, bignumber.js@1.0.1)

C:\xampp\htdocs\officeball\node_scripts>node index.js
application initialized
server module initialized
login module initialized
validator module initialized

module.js:340
    throw err;
          ^
Error: Cannot find module 'mysql'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (C:\xampp\htdocs\officeball\node_scripts\custom_module
s\db_connect.js:1:80)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)

C:\xampp\htdocs\officeball\node_scripts>node index.js
application initialized

module.js:340
    throw err;
          ^
Error: Cannot find module 'mysql'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (C:\xampp\htdocs\officeball\node_scripts\index.js:4:18
)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)

C:\xampp\htdocs\officeball\node_scripts>node index.js
application initialized
server module initialized
login module initialized
validator module initialized

module.js:340
    throw err;
          ^
Error: Cannot find module 'mysql'
    at Function.Module._resolveFilename (module.js:338:15)
    at Function.Module._load (module.js:280:25)
    at Module.require (module.js:364:17)
    at require (module.js:380:17)
    at Object.<anonymous> (C:\xampp\htdocs\officeball\node_scripts\custom_module
s\db_connect.js:1:80)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)

C:\xampp\htdocs\officeball\node_scripts>

我犯了什么新手错误？

Answer 1

您要npm install mysql ，而不要npm install node-mysql

第一个将安装此模块 ，第二个将安装另一个 模块 。

请注意，查看控制台输出后，您会看到node-mysql将安装mysql ，但这仅是内部依赖项。

您-经验法则what应该是相同的字符串

命令行：

npm安装什么

JavaScript代码

var what = require('what');

Answer 2

您将npm软件包名称弄糊涂了（可以理解，在这种情况下，这很令人困惑）。 npm软件包名称和您传递给require的名称将始终完全匹配，但这并不意味着github存储库将是相同的名称。 我想您想做： npm install --save mysql ，它将为您提供mysql软件包，该软件包恰好位于名为node-mysql的github存储库中。 碰巧和烦恼的是，还有一个完全不同的名为node-mysql npm软件包（它违反了约定和公民的敏感性，但无论如何），我怀疑这是您想要的软件包。

您还应该执行npm uninstall node-mysql来清除以前的错误。