检查用户是否存在node.js mysql

npm install mysql

const mysql = require('mysql');

// 创建与MySQL数据库的连接
const connection = mysql.createConnection({
  host: 'localhost',
  user: 'your_username',
  password: 'your_password',
  database: 'your_database'
});

// 连接到MySQL数据库
connection.connect();

// 查询用户是否存在
const username = 'your_username';
const query = `SELECT * FROM users WHERE username = '${username}'`;

connection.query(query, (error, results) => {
  if (error) throw error;

  if (results.length > 0) {
    console.log('用户存在');
  } else {
    console.log('用户不存在');
  }
});

// 关闭与MySQL数据库的连接
connection.end();