Question

我试图找到一个用户是否存在于给定电子邮件和密码的表中，但是我无法使该函数返回正确的值（当前返回“false”），而函数内部的警报确实存在（警报） “真正”）。

如何添加回调函数以使其作为同步过程工作，以便如果用户存在，则结尾的return语句为true？

export const onSignIn = (em, pw) => {

    var authorized = false;
    db.transaction( tx => {
        tx.executeSql(
        `select * from users where email = ? and password = ?;`,
        [em, pw],
        function (transaction, result){
          if (result != null && result.rows != null) {
              for (var i = 0; i < result.rows.length; i++) {
                  var row = result.rows.item(i);
                  if((row.email === em) && (row.password === pw)){
                    authorized = true;
                    alert(authorized)
                  }
              }
          }

        });
    });


    return authorized
}

Answer 1

export const onSignIn = (em, pw, callback) => {
    db.transaction( tx => {
        tx.executeSql(
        `select * from users where email = ? and password = ?;`,
        [em, pw],
        function (transaction, result){
          if (result != null && result.rows != null) {
              for (var i = 0; i < result.rows.length; i++) {
                  var row = result.rows.item(i);
                  if((row.email === em) && (row.password === pw)){
                    callback(true);
                    alert(authorized);
                    return; // ignore the other results
                  }
              }
          }
          // either no results or results does not contain em,pw
          callback(false);
        });
    });


    return authorized
}

然后你会使用这个函数：

onSignIn('user', 'pass', function(success){
  if (success) {
     // code for successful sign in
  } else {
     // code for failed sign in
  }
});

Node.js为sqlite事务添加回调函数

1 个答案: