CODEWITHSUNDEEP
javascriptmysqlnode.jsdiscord.js
AdamDaze
AdamDaze

Reputation: 11

Node.js : On SQL query that returns no record : TypeError: Cannot read property of undefined

UPDATE : GOT IT WORKING See bottom.

I've got this little script going to make a SQL query using node.js, using a variable supplied by a user in a discord channel (upperArgs). The idea is it prints found data in console, and prints "No record" in console if the query comes up null.

Works great if the query finds a record, but if it doesn't I still get

TypeError: Cannot read property 'registered_owner' of undefined

I've tried a range of solutions like splitting the concat into two separate queries and more, but I can't seem to get this error to stop throwing.

client.on('message', async message => {
	//Then ignores them if they are from another bot. 
if (message.author.bot) return;
  // Or if they don't have our specified prefix
if (message.content.indexOf(config.prefix) !== 0) return;
	// Or if they aren't in our specified channel
if (message.channel.id === (config.channelid)) {

	// Strips prefix, lowercases command, uppercases args to match db value.
const args = message.content.slice(config.prefix.length).trim().split(/ +/g);
const command = args.shift().toLowerCase();
const upperArgs = args.map(arg => arg.toUpperCase());

var platequery = "SELECT CONCAT(firstname,' ', lastname) AS registered_owner FROM essentialmode.users where identifier = (Select owner FROM essentialmode.owned_vehicles where plate = '" + upperArgs + "')";

if (command === 'check') {

    var tag = await con.query(platequery, function(err, result) {
      if (err) throw err
      if (tag !== undefined)
      {
       var platedata = (result[0].registered_owner);
        console.log(platedata);
      }
      else console.log("Not found")
    });
  }
}
});

UPDATE : GOT IT WORKING using result.length

if (command === 'check') {

    var tag = await con.query(platequery, function(err, result) {
      if (err) throw err
      if (result.length > 0) {
        if (result)
          console.log("Registerd to " + result[0].registered_owner)
      }
      else console.log('Stolen');
    });
  }

Upvotes: 1

Views: 1504

Answers (2)

AdamDaze
AdamDaze

Reputation: 11

if (command === 'check') {

    var tag = await con.query(platequery, function(err, result) {
      if (err) throw err
      if (result.length > 0) {
        if (result)
          console.log("Registerd to " + result[0].registered_owner)
      }
      else console.log('Stolen');
    });
  }

Upvotes: 0

Cody Geisler
Cody Geisler

Reputation: 8617

You should check if result has a [0] element before trying to access its properties, and then check if registered_owner is in result[0].

Alternatively, you could use something like lodash and do _.get(result,'[0].registered_owner',null)

  if (typeof tag !== "undefined")
  {
   var platedata = result.length > 0 
     ? 'registered_owner' in result[0]
       ? (result[0].registered_owner) 
       : null
     : null ;
   console.log(platedata);
  }

Upvotes: 1

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