How do I return callback of MySQL query and push to an array in Node.js?

Question

I'm trying to populate an array using a MYSQL query on a table that takes all rows and pushes the rows to WordList.

I can print each line within the method fine, but when I go out of the scope of that method it doesn't push anything to Wordlist.

function getParrotMessage() {

    wordList = [];

    console.log(wordList);

    // Implementation
    getWord('result', function (err, result) {

        console.log(result); // works, prints the row data in MySQL table
        wordList.push(result); // doesn't work

    });

    console.log(wordList);
    return parrot_message;
}

// Method
function getWord(word, callback) {
    var query = con.query('SELECT * FROM word_table');
    query.on('result', function (row) {
        callback(null, row.word);
    });
};

wordlist: []

wordlist shows up as an empty array.

Any help would be greatly appreciated, just beginning with javascript and node.js

Your method getWord is asynchronous ! So the second console.log(wordList); is printed before any results are returned (before you even call wordList.push(result); for the first time) — Molda
– Molda, Commented Nov 16, 2016 at 19:10
So how can I actually retrieve that result data so I can manipulate it and do various other thing. I don't need to print it. — user1920076
– user1920076, Commented Nov 16, 2016 at 20:53

Molda · Accepted Answer · 2016-11-16 21:42:33Z

Your method getWord is asynchronous!

So the second console.log(wordList); is printed before any results are returned (before you even call wordList.push(result); for the first time)

Also since you query db(which is asynchronous) in getParrotMessage function you need to use callback (or Promise or whatever else there is that can be used) instead of return statement.

function getParrotMessage(callback) {

    getWord('result', function (err, result) {

        if(err || !result.length) return callback('error or no results');
        // since result is array of objects [{word: 'someword'},{word: 'someword2'}] let's remap it
        result = result.map(obj => obj.word);
        // result should now look like ['someword','someword2']
        // return it
        callback(null, result);

    });
}

function getWord(word, callback) {
    con.query('SELECT * FROM word_table', function(err, rows) {
        if(err) return callback(err);
        callback(null, rows);
    });
};

now use it like this

getParrotMessage(function(err, words){
    // words => ['someword','someword2']

});

Collectives™ on Stack Overflow

How do I return callback of MySQL query and push to an array in Node.js?

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related