如何返回对象而不是数组？

Question

I was trying to return a JSON Object but instead it returns an array. I am using primary key for query so I am sure I will only get one result.

This is my approach :

router.get("/student_info/:id", (req, res, next) => {
    connection.getConnection((error, currentConnection) => {
        if (!!error) {
            console.log("Error occurred while connecting db")
        } else {
            let id = req.params.id;
            currentConnection.query("SELECT * FROM students WHERE id=" + "'" + id + "'", (error, rows, fields) => {
                if (!!error) {
                    console.log(error.message)
                } else {
                    res.status(200).json(rows);
                }
                currentConnection.release();
            });
        }
    });
});

What I want is this :

    {
        "id": "171-15-8966",
        "name": "Alif Hasnain",
        "course_code": "CSE412,CSE413"
    }

But I get the result like this :

[
    {
        "id": "171-15-8966",
        "name": "Alif Hasnain",
        "course_code": "CSE412,CSE413"
    }
]

Answer 1

只需在 json 转换之前获取数组的第一个元素：

res.status(200).json(rows[0]);

Answer 2

By default query return the array of rows reflected by the select query. Since your query has single result it returns as array of single object to user.

You can change it to

res.status(200).json(rows[0]);

Please let us know if got better alternate.

Answer 3

Try this, using nested array destructuring

res.status(200).json([[rows]]);

You can read this blog to learn more about ES6 - Destructuring

ES6 - Understanding Destructuring