functionscope.js

myStuff.forEach(function stuff){
    
    var subStuff = stuff.subStuff;

    doSomething({

        success: (function(subStuff) { // creates a function scope
            return function(results) { // the actual success callback with subStuff scoped
                // subStuff and results are now function scoped
            };
        })(subStuff); // immediately invoke the function.

    });

});

myStuff.forEach(function stuff){

    var subStuff = stuff.subStuff;

    doSomething({

        success: (function(subStuffScoped) { // creates a function scope
            return function(results) { // the actual success callback with subStuff scoped
                // subStuffScoped and results are now function scoped
            };
        })(subStuff); // immediately invoke the function.

    });

});