Question

I have the following in the routing for my nodejs app, but it runs twice each time and tries sending both files. How do I stop it from running twice.

        app.get('/', function(req, res){
            data =  validate(req.cookies.user,req.cookies.code,function(data) {         
                    if (data == 'false'){
                            console.log('send to login');
                            res.sendFile(__dirname + '/views/login.html');
                    }
                    else {
                            console.log('send to chat');
                            res.sendFile(__dirname + '/views/chat.html');
                    }
                    console.log('USER DATA'+data);
            });

    });

First run works fine, and needs to stop there. But it auto runs a second time and undefined the results.

It calls the following function, which is a work in progress.

      function validate (user, code, callback) {
            con.query(
                  "SELECT * FROM tbl_users WHERE id = "+con.escape(user)+" and code = "+con.escape(code),
                   function(err,results) {
                            console.log('Validation Access');
                            console.log('User: '+user+' Code: '+code);
                            for (row in results) {
                                    data = results[row];
                                    console.log('Userdata: '+data);
                                    if(data.id) {
                                     console.log('Account Found');
                                            callback(data);
                                    }
                            }
                            console.log('Not Found');
                            callback('false');

                    }
            );
    }

The terminal output from the logging is

Express server listening on port 3000
Validation Access
User: 1 Code: 0
Userdata: [object Object]
Account Found
send to chat
USER DATA[object Object]
Not Found
send to login
USER DATAfalse

On looking at other posts there are no working answers

Answer 1

问题是，即使找到了帐户，您的查询处理程序始终也会调用callback('false');。解决该特定问题的最简单方法是在内部回调之后插入return语句，如下所示：

                        for (row in results) {
                                data = results[row];
                                console.log('Userdata: '+data);
                                if(data.id) {
                                 console.log('Account Found');
                                        callback(data);
                                        return; // prevent second callback
                                }
                        }
                        console.log('Not Found');
                        callback('false');

Preventing Double running on NodeJS

1 个答案: