D:\le\node_modules\mysql\lib\protocol\Parser.js:

        throw err; // Rethrow non-MySQL errors

        ^

Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the cli

ent

    at ServerResponse.setHeader (_http_outgoing.js::)

    at ServerResponse.header (D:\le\node_modules\express\lib\response.js::

)

    at ServerResponse.send (D:\le\node_modules\express\lib\response.js::

)

    at ServerResponse.json (D:\le\node_modules\express\lib\response.js::

)

    at ServerResponse.send (D:\le\node_modules\express\lib\response.js::

)

    at D:\le\routes\cart.js::

    at D:\le\models\cart.js::

    at Query._callback (D:\le\models\db.js::)

    at Query.Sequence.end (D:\le\node_modules\mysql\lib\protocol\sequences\Se

quence.js::)

    at Query.ErrorPacket (D:\le\node_modules\mysql\lib\protocol\sequences\Que

ry.js::)

npm ERR! code ELIFECYCLE

npm ERR! errno

npm ERR! letao@0.0. start: `node ./bin/www`

npm ERR! Exit status

npm ERR!

npm ERR! Failed at the letao@0.0. start script.

npm ERR! This is probably not a problem with npm. There is likely additional log

ging output above.

npm ERR! A complete log of this run can be found in:

npm ERR!     C:\Users\administrator\AppData\Roaming\npm-cache\_logs\--28T11_00_46_4

81Z-debug.log

D:\letao>

    pool.getConnection(function(err, connection) {

        if (err) {

            // callback(err);

            return callback(err);

        }

        connection.query(sqlStr, params, function(err, rows) {

            if (err) {

                // callback(err);

                return callback(err);

            }

            connection.release();

            callback.apply(null, arguments);//报错行44

        });

    });