nodejs防止sql注入的方法：
1.使用escape()对传入参数进行编码，例如：
var userId = 1, name = 'test';
var query = connection.query('SELECT * FROM users WHERE id = ' + connection.escape(userId) + ', name = ' + connection.escape(name), function(err, results) {
// ...
});
console.log(query.sql); // SELECT * FROM users WHERE id = 1, name = 'test'
2.使用connection.query()的查询参数占位符，例如：
var userId = 1, name = 'test';
var query = connection.query('SELECT * FROM users WHERE id = ?, name = ?', [userId, name], function(err, results) {
// ...
});
console.log(query.sql); // SELECT * FROM users WHERE id = 1, name = 'test'
3.使用escapeId()编码SQL查询标识符，例如：
sorter = 'date';
var sql = 'SELECT * FROM posts ORDER BY ' + connection.escapeId(sorter);
connection.query(sql, function(err, results) {
// ...
});
4.使用mysql.format()转义参数，例如：
userId = 1;
var sql = "SELECT * FROM ?? WHERE ?? = ?";
var inserts = ['users', 'id', userId];
sql = mysql.format(sql, inserts); // SELECT * FROM users WHERE id = 1
