Push value in an empty array from a function

I am retrieving some JSON data from an API using Jquery AJAX and I want to change the URL dynamically on checkbox selection. I have four checkbox and I want to store checkbox value to an globle array. When I put console.log(category) or ajax code inside function its working but when I put the code outside the function its not working.

var category = [];
    $(".ckbox").click(function() {
      if($(this).is(":checked")) {
        category.push($(this).val());
      } else {
        var x = category.indexOf($(this).val());
        category.splice(x, 1);
      }
    });

    $.ajax({
            url: 'https://godrejapi-dot-indiacomapi.appspot.com/_ah/api/godrej/v1/godrejestablishment?',
            dataType: 'json',
            type: 'GET',
            data: {
              category: category, //I wnat to change this
              city: 'PUNE',
              begin: '0',
              limit: '200',
            },
            traditional: true,
            success: function(response){
              // console.log(response);
            },
            error: function(err){
              alert("something went wrong.");
              console.log(err);
            }
        });

Code (JavaScript):

 

Because the category is local in scope to the function. You'll have to put the ajax code inside the function

 

When I put ajax code inside the function, it's working but I want ajax code outside. I want to store the value of category to a global variable, So I can access it in ajax code and I can't figure out how to do that.