Why is my pg-query result throwing a TypeError

Question

I am creating a node function to create a user in a PostgreSQL database. I'm using node.js, pg and pg-query to communicate from the app to the database.

Before I insert a new record Im trying to validate the email address does not already exist.

I am not sure why my result.rows[0].id is throwing a TypeError: Cannot read property '0' of undefined error Based on the documentation I am using the correct syntax to access the results of my query.

This is the function:

/* POST create user */
router.post('/adduser', function(req, res) {

    var salt = crypto.randomBytes(16);
    var newHash = hash(req.body.password, salt);

    query.connectionParameters = connString;
    query('SELECT id FROM users WHERE email = $1',[req.body.email], function(err, result) {
    if (err){
        console.log('Insert error: ' + err);
    }

    // If email exists, return error else insert new record
    if(result.rows[0].id != null) {
        query('INSERT INTO users (email, password, salt) VALUES ($1, $2, $3)', [req.body.email, newHash, salt], function(err, result) {
              if (err){
                console.log('Insert error: ' + err);
              }
              res.send( ( err === null ) ? { msg: '' } : { msg:err }  );
            });
    }
    else{
        console.log(result);
        res.send({msg:'User already exists'});
    }
    });
});

And the error I am receiving is as follows:

/home/robot/workspace/userapp/routes/users.js:35
    if(result.rows[0].id != null) {
                  ^
TypeError: Cannot read property '0' of undefined
    at /home/robot/workspace/userapp/routes/users.js:35:23
    at Function.onSuccess (/home/robot/workspace/userapp/node_modules/pg-query/index.js:55:7)
    at null.callback (/home/robot/workspace/userapp/node_modules/pg-query/node_modules/okay/index.js:7:16)
    at Query.handleReadyForQuery (/home/robot/workspace/userapp/node_modules/pg/lib/query.js:80:10)
    at null.<anonymous> (/home/robot/workspace/userapp/node_modules/pg/lib/client.js:158:19)
    at emit (events.js:129:20)
    at Socket.<anonymous> (/home/robot/workspace/userapp/node_modules/pg/lib/connection.js:109:12)
    at Socket.emit (events.js:107:17)
    at readableAddChunk (_stream_readable.js:163:16)
    at Socket.Readable.push (_stream_readable.js:126:10)

I'm new to javascript and node so it may be something very obvious. Here is the pg-query documentation if it helps.

** SOLUTION **

Changing the conditional to if(result[0].num == 0) { solved the problem. pg-query does not return a property called rows apparently.

Answer 1

It looks to me like the rows object is undefined to indicate that there are no users with the given email address. You could change the query to select count(*) as num from users where email = $1. This would ensure a result, and you can test if result.rows[0].num == 0.

Answer 2

** SOLUTION **

Changing the conditional to if(result[0].num == 0) { solved the problem. pg-query does not return a property called rows apparently.