How to pass additional arguments to callback funct

Question

I'm working with javascript for Google Analytics API but I'm no more than a novice in JS. I have C++ and Java knowledge and I can get along with logical thinking but some things puzzle me. In GA API I get to make a function call like this:

gapi.client.analytics.data.ga.get({'ids':'<tableID>',
    'start-date':'<startDate>',
    'end-date':'<endDate>',
    'metrics':'<metrics>',
    'filters':'<filters>',
    'samplingLevel':'HIGHER_PRECISION',}).execute(putToVar);

putToVar() is a user defined function defined like so:

function putToVar(results)
{
    //do processing with the results
}

It is my understanding that the .execute() method is used to invoke a callback function for the asynchronous call gapi.client.analytics.data.ga.get(). So I assume what function1().execute(function2) does is call function2 with the return value from function1 as argument? Is this correct?

I'm in a situation where I need to apply several distinct filters and store them in an array to retrieve as and when required, irrespective of whether the API call returned a results object (it is an async call, so I don't know when the response comes, it is only visible to the callback function).

I would like to pass to the callback function the dimensions of the array in which to store the returned objects so that I can retrieve them on demand later, without worrying about the order in which the responses get processed. I say this because, initially I tried a for loop and the order in which I got the response to my API calls were not the same as the order in which I placed API calls for my queries, so there were mismatches.

Since the reference uses this method to invoke the callback function, I would like to know how to pass additional arguments to a callback function like this when using .execute() method, when I get to write putToVar() function something like this:

function putToVar(results,arrayDim)
{
    //Process Results
    //Store in Array[arrayDim] the required value
}

I hope I have made myself clear. I have read the following posts

• How do I pass multiple arguments into a javascript callback function?
• passing arguments to callback
• How to explain callbacks in plain english? How are they different from calling one function from another function?
• How to pass additional arguments to callbacks and also access default parameters?

but none of them seem to use the .execute() method and I cannot figure out how to use what they have said. Or, if and how my .execute() method (type of callback execution) can be modified to help my purpose.

Answer 1

Adding a closure would solve your problem:

for(var x = 0; x< n x ++){  //Or any other loop
   (function(x){   //Closure. This line does the magic!!
       var arrayDim = something_that_depends_on_x_or_the_loop,
           param2 = some_other_thing_that_depends_on_x;
       gapi.client.analytics.data.ga.get({'ids':'<tableID>',
         'start-date':'<startDate>',
          ...
       }).execute(function putToVar(results){   //this fn is defined inline to get access to param1, param2
           //The following alerts will use the *correct* variables thanks to the closure
           alert(x);
           alert(arrayDim);
           alert(param2);
       });
   })(x); //This one too
}

The closure does the magic. It will allow to each loop cycle to have its own variables (not shared), so the proper ones will be inside putToVar when executed.

I hope it's clear, if not, just let me know.

Just test it!

Cheers, from La Paz, Bolivia