[英]Node.js throwing TypeError: Cannot read property 'testModule' of undefined
[英]Node.js TypeError: Cannot read property 'host' of undefined
我是一个 node.js 和 MySQL 初学者,我刚刚开始设置并尝试一些基本代码。当我按照本教程练习时,“ https://medium.com/@ekkodo/node-js-restful-web-api -%E7%AF%84%E4%BE%8B-for-mysql-d8be860594c1 ”, 终端显示“TypeError: Cannot read property 'host' of undefined”错误,无法连接MySQL。
(程序中的“Product”是我数据库中的一个表名)
This is the error displayed on my terminal
PS C:\Users\CJSCOPE\Desktop\nodetest\webapi> node app.js
C:\Users\CJSCOPE\Desktop\nodetest\webapi\node_modules\mysql\lib\ConnectionConfig.js:12
this.host = options.host || 'localhost';
^
TypeError: Cannot read property 'host' of undefined
at new ConnectionConfig (C:\Users\CJSCOPE\Desktop\nodetest\webapi\node_modules\mysql\lib\ConnectionConfig.js:12:37)
at Object.createConnection (C:\Users\CJSCOPE\Desktop\nodetest\webapi\node_modules\mysql\index.js:13:34)
at Object.<anonymous> (C:\Users\CJSCOPE\Desktop\nodetest\webapi\models\product.js:4:24)
at Module._compile (internal/modules/cjs/loader.js:1128:30)
at Object.Module._extensions..js (internal/modules/cjs/loader.js:1167:10)
at Module.load (internal/modules/cjs/loader.js:983:32)
at Function.Module._load (internal/modules/cjs/loader.js:891:14)
at Module.require (internal/modules/cjs/loader.js:1023:19)
at require (internal/modules/cjs/helpers.js:72:18)
at Object.<anonymous> (C:\Users\CJSCOPE\Desktop\nodetest\webapi\routes\product.js:2:15)
app.js
var bodyparser = require('body-parser');
var express = require('express');
var config = require('./config');
var functions = require('./function');
var product =require('./routes/product');
var app=express();
req.body
app.use(bodyparser.urlencoded({ extended:false }));
app.use(bodyparser.json());
app.use(functions.passwordCrypto);
app.use('./product',product);
app.listen(config.port, function(){
console.log('app listening on port'+ config.port + '!');
});
product.js(models)
var mysql =require('mysql');
var config =require('../config');
var connection = mysql.createConnection(config.db);
var sql = '';
module.exports = {
item:function(req,callback){
sql = 'SELECT * FROM product';
return connection.query(sql,callback);
},
item:function(req,callback){
sql = mysql.format('SELECT * FROM product WHERE id= ?',[req.params.id]);
return connection.query(sql,callback);
},
add:function(req,callback){
console.log('req.body',req.body);
sql = mysql.format('INSERT INTO product SET ?',req.body);
return connection.query(sql,callback);
},
delete:function(req,callback){
sql = mysql.format('DELETE * FROM product WHERE id= ?',[req.params.id]);
return connection.query(sql,callback);
},
put:function(req,callback){
connection.beginTransaction(function(err){
if(err) throw err;
sql=mysql.format('DELETE * FROM product WHERE id= ?',[req.params.id]);
connection.query(sql,function(err,results,fields){
if(results.affectedRows){
req.body.id=req.params.id;
sql=mysql.format('INSERT INTO product SET ?',req.body);
connection.query(sql,function(err,results,fields){
if(err){
connection.rollback(function(){
callback(err, 400);
});
}else{
connection.commit(function(err){
if(err) callback(err,400);
callback(err,200);
});
}
});
}else{
callback(err,410);
}
});
});
},
patch:function(req,callback){
sql = mysql.format('UPDATE product SET ? WHERE id = ? ',[req.body, req.params.id]);
return connection.query(sql,callback);
}
}
product.js(routes)
var express = require('express');
var product = require('../models/product');
var router=express.Router();
router.route('/')
.get(function (req,res){
product.items(req, function(err, results, fields){
if(err){
res.sendStatus(500);
return console.error(err);
}
if(!results.length){
res.sendStatus(404);
return;
}
res.json(results);
});
})
.post(function(req,res){
product.add(req, function(err,results,fields){
if(err){
res.sendStatus(500);
return console.error(err);
}
res.status(201).json(results.insertId);
});
});
router.route('./id')
.get(function(req,res){
product.item(req,function(err,results,fields){
if(err){
res.sendStatus(500);
return console.error(err);
}
if(!results.length){
res.sendStatus(404);
return;
}
res.json(results);
});
})
.delete(function (req,res){
product.delete(req,function(err,results,fields){
if(err){
res.sendStatus(500);
return console.error(err);
}
if(!results.affectedRows){
res.sendStatus(410);
return;
}
res.sendStatus(204);
});
})
.put(function(req,res){
product.put(req,function(err,results){
if(err){
res.sendStatus(500);
return console.error(err);
}
if(results === 410){
res.sendStatus(410);
return;
}
product.item(req,function(err,results,fields){
res.json(results);
});
});
})
.patch(function(req,res){
product.patch(req,function(err,results){
if(err){
res.sendStatus(500);
return console.error(err);
}
if(!results.affectedRows){
res.sendStatus(410);
return;
}
req.body.id=req.params.id;
res.json([req.body]);
});
});
module.exports = router;
function.js
var crypto = require('crypto');
var config = require('./config');
module.exports = {
passwordCrypto: function(req,res,next){
if(req.body.password){
req.body.password=crypto.createHash('md5')
.update(req.body.password+config.salt)
.digest('hex');
}
next();
}
};
config.js
module.export = {
db:{
host:'127.0.0.1',
user:'root',
password:'1234',
database:'shop',
port:3306
},
port:3300
}
这是您需要通过传递所有必需的婴儿车为 mysql 创建连接对象的方式,示例:
var config =require('../config');
const connection = mysql.createConnection({
host: config.db.host,
user: config.db.user,
password: config.db.password,
database: config.db.database
});
确保路径var config =require('../config');
是正确的,您可以通过将其悬停来阅读该文件。
也改变module.export = {
到module.exports = {
在config.js
文件
我认为问题是你在config.js
有一个错字。 您正在使用module.export
而不是module.exports
,因此您不会导出任何内容,并且当您在product.js
使用require()
时,您会得到一个空对象,因此config.db
是undefined
。
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