Why JavaScript var change?

Question

Hi I'm loading a JSON file with JavaScript like this:

 var cvalue=[];

 var i =0;
 $.getJSON('cities.json', function(json) {
  $.each(json.value.Map, function(index, value) {

     cvalue[i]= {
          text: index,
          size: this.oneMinuteRate*20
      };

     i++;
  });

But then when I try to use the var outside from these functions, cvalue has a different structure and I would to keep the previous. Any hint?