How to pass parameters to mysql query callback in nodejs

user_1368599 0
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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?

node.js callback mysql
4 Answers

MySQL con.query has overloaded function. Inside of callback you use global variable or any variable that is passed into your function parameter. For example:

Example 1: it takes sql string and callback function

var adr = 'Mountain 21';
var sql = 'SELECT * FROM customers;
con.query(sql, function (err, result) {
  if (err) throw err;
  console.log(adr);
});

Example 2: it takes sql string, parameter and callback function

var adr = 'Mountain 21';
var sql = 'SELECT * FROM customers WHERE address = ?';
con.query(sql, [adr], function (err, result) {
  if (err) throw err;
  console.log(adr);
});
user_71199040
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