Two small problems in creating user registration interface

        Today, when creating the user registration interface , There are two small problems ：① Use the method of traversing the object to determine whether the received data is empty ;② Determine whether the user name already exists . After repeated attempts , Finally found a solution , Now share with you ！

One 、 The method of traversing the object determines whether the requested data is empty

        This problem is to solve when users register , You need to insert the received data into the database , But when inserting the database , You must first judge whether the user has filled in the user information , So you need to judge whether it is empty .

        At first , When solving this problem, I think of using if-else Judge , By judging whether the attribute value of each attribute in the obtained object is empty , To solve this problem , And it also realizes this function , But later found , This method is complicated , All consider using traversal arrays , Implement this function .

        Don't talk much , Go straight to the code ：

var obj = req.body;
    var count = 400;
    for (var k in obj) {
        console.log(k, obj[k])
        count++;
        if (!obj[k]) {
            res.send({ code: count, msg: `${k} Can't be empty ` });
            return;
        }
    }
    if (!/^1[3-9]\d{9}$/.test(obj.phone)) {
        res.send({ code: 405, msg: 'phone Format error ' });
        return;
    }

        Here's the thing to note ： If you have to judge other conditions , The judgment sentence must be written for..in Outside , This time, I suffered a big loss here .

Two 、 Determine whether the user name already exists

        When the user is entering a user name , You need to judge whether the following user names have been occupied , So I thought of querying the data in the database uname Is it equal to the received uname, But I made some small mistakes when trying to realize this idea , Led to bug.

        Because it needs to be judged after querying the database , To get the result Is it empty , If it is empty , Direct response “ The user already exists ”, Then jump out of the function body .

         Next on the code ：

// establish sql command , Query whether the user name exists 
    pool.query('select * from xz_user where uname=?', [obj.uname], (err, result) => {
        if (err) throw err;
        if (result.length) {
            res.send({ code: 406, msg: ' User name already exists ' })
            return;
            // Want to achieve   Determine whether the user name already exists , By querying whether the database exists uname= Currently requested uname
            // After getting the results , Want to end directly and respond to the result    But there is a problem of secondary response 
        }
        // establish sql command , Insert database 
        pool.query('insert into xz_user set ?', [obj], (err, result) => {
            if (err) throw err;
            res.send({ code: 200, msg: ' User registration successful ', data: result })
        })
    });

        When writing the query and insert commands , There is a problem of secondary response , Later, it was found that the insertion command should be placed in the query statement , In this way, we can make return Jump out of this interface function .

        But if you write the two commands separately , When the program finishes executing the query statement , After executing the query command ,return Just jump out of the query function , I will continue to execute the interrupted order , So it leads to the problem of secondary circulation .

Correct code ：

  My error cases ：