node.js async waterfall for each in array

Question

I have this app that allows users to review movies, and I'm trying to add a feature that grabs the poster from the movie and displays it next to the review. I tried to do this using

query database and return list of movies => imdb-id to get the IMDB ID => imdb to get the poster url => add that to a variable and compile with pug

However, I can't get it to work as the array always returns empty first before anything else runs. I've tried to use async waterfall, but I can't figure out how to loop through the array that is returned, and pass the ID to get the url

async.waterfall([
    function (callback) {
        console.log('Request Id:', username);
        var query = "SELECT title, rating, review FROM movies WHERE username = \"" + username + "\" ORDER BY title;";
        callback(null, query);
    }, function (query, callback) {
        // Run query on db
        connection.query(query, callback);
    }, function (rows, fields, cb) {
        // Get array of titles
        var rowArray = rows;
        console.log(rowArray);
    }
],
function(err) {
    // error stuff
})

I am aware that this is also async, however I was speaking about the native async / await which is literally syntactic sugar for promises. I am not sure what node verison / es version you are targeting, so I can't tell you if can use it at all. If you can I can recommend you to use it, as it makes the code a lot more readable. — kentor
– kentor, Commented Nov 29, 2017 at 1:28
Oh okay. I think I'm actually going to do this with AJAX instead, it would make things a lot easier. Thanks anyways! — Ryan Knutson
– Ryan Knutson, Commented Nov 29, 2017 at 1:30
What? You provided node.js as tag which means you are talking about backend code here. You usually never run db queries from the frontend. Anyways I am posting an answer to explain how you could have solved it. That should help for front- and backend programming. — kentor
– kentor, Commented Nov 29, 2017 at 1:32

kentor · Accepted Answer · 2017-11-29 01:35:38Z

1

I recommend you to use promises or the es2017 async/await instead.

Side note: The first block in your async waterfall is synchronous anyways and you don't perform any lengthy operations there. You could merge the connection.query row into it.

With async/await your code could look like this:

async function sendQuery() {
  console.log('Request Id:', username);
  const query = "SELECT title, rating, review FROM movies WHERE username = \"" + username + "\" ORDER BY title;";

  try {
    const rows = await connection.query(query);
    console.log(rowArray);
  } catch(err) {
     console.log(err);
  }
}

answered Nov 29, 2017 at 1:35

kentor

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