JavaScript的MySQL和承诺

Question

我正在与承诺，或至少尝试。

这里是我的代码看起来是迄今：

checkEmailUsername = function(mail, user) { 
    return new Promise(function(resolve, reject) { 
     var query; 
     query = "SELECT * FROM users WHERE email = ? OR username = ?"; 
     return connection.query(query, [mail, user], function(err, row, fields) { 
     if (err) { 
      reject(err); 
     } 
     console.log(row.length); 
     if (row.length > 0) { 
      return resolve(true); 
     } else { 
      return resolve(false); 
     } 
     }); 
    }).then()["catch"](); 
    }; 

问题。如何从promise中返回解析值？

Answer 1

您不能在这里使用return，使用promise解析函数将db中的行返回给调用者。

checkEmailUsername = function (mail, user) { 
     return new Promise(function (resolve, reject) { 
      var query; 
      query = "SELECT * FROM users WHERE email = ? OR username = ?"; 
      connection.query(query, [mail, user], function (err, row, fields) { 
       if (err) { 
        reject(err); 
       } 
       console.log(row.length); 
       resolve(row); 
      }); 
     }; 

     checkEmailUsername(mail, user).then(function (rows) { 
      // do something with the rows 
     }).catch((err) => { 
      //handle error 
     }