Question

这让我困惑了一段时间，真的不知道发生了什么。我使用node-mysql模块从MySQL获取数据，当结果准备就绪时，我将控制台记录它们并清楚地看到结果。

var sql = 'SELECT \
id, username, first_name, last_name \
FROM users\
WHERE username = ' + mysql.escape(req.params.username) + '';

pool.query(sql, function(err, result) {
  if (err) throw err;
  console.log(result[0]); //Object that contains all the fetched fields
  if ((result[0].username).toLowerCase() == (req.params.username).toLowerCase()) {
    console.log("We got a username!");
    profile.userData = result[0];
    profile.isAvailable = true;
    profile.theme = getProfileSexTheme(profile.userData.sex);
  } else {
    console.log("We dont have a username");
  }
  renderPage(profile);
});

实际错误：

TypeError: Cannot read property 'username' of undefined
    at Query.<anonymous> (/var/www/vhosts/MyWebApp/routes/profile.js:24:23)
    at Query._callback (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/Pool.js:134:8)
    at Query.Sequence.end (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/sequences/Sequence.js:78:24)
    at Query._handleFinalResultPacket (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/sequences/Query.js:143:8)
    at Query.EofPacket (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/sequences/Query.js:127:8)
    at Protocol._parsePacket (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/Protocol.js:202:24)
    at Parser.write (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/Parser.js:62:12)
    at Protocol.write (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/protocol/Protocol.js:37:16)
    at Socket.<anonymous> (/var/www/vhosts/MyWebApp/node_modules/mysql/lib/Connection.js:72:28)
    at Socket.EventEmitter.emit (events.js:95:17)

（profile.js：24就是这条线 if ((result[0].username).toLowerCase() == (req.params.username).toLowerCase()) {）

从控制台日志中，我得到：

{ id: 24,
  username: 'Anna304',
  first_name: 'Anna',
  last_name: 'Pell' }
We got a username!

(These gets don't come from the console log but from node)
GET /profile/Anna304 77ms
GET /profile/style.css 80ms

undefined

那是如何定义的？如果我评论console.log(result[0])，它就不会出现，但是这个控制台日志实际上输出了包含查询结果的对象（就在我们可以看到的GET之前）。

我也尝试在加载页面后通过AJAX调用查询，并且它有效（但我想通过后端进行初始页面加载）。

有关如何进一步解决此问题的任何提示？

TypeError：无法读取undefined |的属性'username'节点和node-mysql

0 个答案: