Correct way to access parent function parameter in inner Javascript callback function

Question

Take the following code snippet.

var exec = require('child_process').exec;

var extraInfo = {'test':1,'passing':'test'};

runWithData(extraInfo);

function runWithData(passedData)
{
    exec('/Users/test/Desktop/testcommand', function callback(error,stdout,stderr)
    {
        if (error)
        {
            console.log("ERROR",stderr);
        }
        else
        {
            console.log(stdout);
        }
    });
}

Within the callback of exec I want to be able to access the passedData. Is accessing passedData direct the correct way to do this and will this get overwritten if multiple function calls are being processed at the same time, or is there a way to attach the info into the callback function so it is tied to it?

This will help: developer.mozilla.org/en/docs/Web/JavaScript/Guide/Closures — techfoobar
– techfoobar, Commented Nov 8, 2014 at 6:41
You can just access 'passedData' directly. It's in a parent scope which is completely accessible to you in the callback. Each function call creates a new scope and thus creates a new set of data so multiple function calls do not mess it up. — jfriend00
– jfriend00, Commented Nov 8, 2014 at 6:51

Paul · Accepted Answer · 2014-11-08 09:11:42Z

1

From @jfriend00:

You can just access 'passedData' directly. It's in a parent scope which is completely accessible to you in the callback. Each function call creates a new scope and thus creates a new set of data so multiple function calls do not mess it up

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