I'm trying to figure out the correct way of passing custom data to a Query call to be made available in the callback. I'm using MySQL library in nodejs (all latest versions).

I have a call to connection.query(sql, function(err, result) {...});

I couldn't find a way to 1) pass custom data/parameter to the call so that 2) it can be made available when the callback is invoked. So what is the proper way of doing so?

I have the following (pseudo-code):

...
for (ix in SomeJSONArray) {
    sql = "SELECT (1) FROM someTable WHERE someColumn = " + SomeJSONArray[ix].id;
    connection.query(sql, function (err, result) {
      ...
      var y = SomeJSONArray[ix].id;
    };
}

From the code above, I need to be able to pass the current value of "ix" used in the query to the callback itself.

How do I do that?

If you are using node-mysql, do it like the docs say:

connection.query(
    'SELECT * FROM table WHERE id=? LIMIT ?, 5',[ user_id, start ], 
    function (err, results) {

    }
);

The docs also have code for proper escaping of strings, but using the array in the query call automatically does the escaping for you.

https://github.com/felixge/node-mysql