Nodejs: Passing function specific variables to Async.parallel()

Question

I am have a bunch of long running database queries I need to get done before I render a page in node. Each of these queries require a few of their own variables. Is there an easy way to pass variables to the async.parallel() utility in nodejs? ``` async.parallel([ queryX(callback, A1, A2, A3), queryX(callback, B1, B2, B3), queryY(callback, C1, C2, C3), queryY(callback, D1, D2, D3), queryZ(callback, E1, E2, E3), queryZ(callback, F1, F2, F3), ], function(err, results) { /*Do Render Stuff with Results*/} ); ```

Accepted Answer

You should respect the callback as last argument nodejs convention when you write functions. That way you could have use Function.bind to call your functions instead.

```
var queryx = function(A,B,C,callback){ .... ; callback(err,result) };

async.parallel([queryx.bind(null,A1,B2,A3),...,],callback);
```

bind returns a partial application :

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Function/bind

Nodejs: Passing function specific variables to Async.parallel()

Solution

Problem