遍历NodeJS中的循环时发生TypeError

Question

I'm trying to write my database-data to a JSON. It works when I do not use the loop.

Then I get: TypeError: first argument must be a string or Buffer

I'm using the mysql npm package.

con.query('SELECT * FROM mydb.orders_view;', function(err, rows, fields) {
            if (err) {
                res.status(500).json({ result: 'Error' })
            }
            for (var i = 0; i < rows.length; i++) {

                 res.write(
                 {
                time: date,
                Order: [{
                    OrderedBy: rows[i]['OrderedBy']
                }]
               } 
            );
                }

            res.end();


        });
});

Answer 1

You're calling write with an object. According to the documentation, it must be a string or buffer:

chunk can be a string or a buffer. If chunk is a string, the second parameter specifies how to encode it into a byte stream. By default the encoding is 'utf8'. The last parameter callback will be called when this chunk of data is flushed.

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Side note: You're not handling the error case properly, you probably want a return; in that initial if block so you don't continue to the loop when an error occurs.