node.js - 将对象分配给node.js中的变量

Question

有人可以解释一下为什么我无法将 rows 对象传递给 Clubs 变量吗？

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : '',
  database : 'test'
});
var competition_feed = 'England';
var season_id = 2014;
var clubs = {};

connection.connect();

connection.query('SELECT * FROM clubs WHERE competition_feed=\''+competition_feed+'\' AND season_id='+season_id+';', function(err, rows, fields) {
    if (err) throw err;
    clubs = rows;
});

console.log(clubs);

connection.end();

我似乎遗漏了一些关于变量和范围的内容。请帮忙:)

Answer 1

你可以，这不起作用的原因是

connection.query(.....)

是异步的。因此，直到事件循环的后期，俱乐部才会设置为行。在您尝试使用它之后。实现您想要的行为的一种方法如下:

var mysql      = require('mysql');
var connection = mysql.createConnection({
  host     : 'localhost',
  user     : 'root',
  password : '',
  database : 'test'
});
var competition_feed = 'England';
var season_id = 2014;
var clubs = {};

connection.connect();

connection.query('SELECT * FROM clubs WHERE competition_feed=\''+competition_feed+'\' AND season_id='+season_id+';', function(err, rows, fields) {
    if (err) throw err;
    clubs = rows;
    logClubs();
});

function logClubs() {
    console.log(clubs);
}


connection.end();