TypeError：res不是一个函数
exports.signup_submit = function(req,res){ console.log(req.body.username,"------------------");
var sql = "INSERT INTO customers (username) VALUES (req.body.username)";
con.query(sql, function (err, result, fields) {
if (err) { return res(err); }
else { return res(result); }
res.render(__dirname + '/views/success.html');
});
res()替换res.end()或渲染：
exports.signup_submit = function(req,res){
console.log(req.body.username,"------------------");
var sql = "INSERT INTO customers (username) VALUES (req.body.username)";
con.query(sql, function (err, result, fields) {
if (err) {
return res.render(__dirname + '/views/error.html');
}
res.render(__dirname + '/views/success.html');
});