.JS while loop fails pushing values onto array [duplicate]

I have this strange scope issue with the while loop below. If I place console.log inside both the function and while loop I get the result I'm looking for, but for the code below I get nothing at all. It seems that the .push method is not pushing the values into the arrays CCY and dts. Any ideas how I can fix this issue?

  var CCY=[]; 
  var dts=[]; 
  var start = new Date(x);
  var end = new Date(y);
  while(start < end){

    var newDate = start.setDate(start.getDate() + 1);
    start = new Date(newDate);
    var d = (start.toISOString().split('T')[0]);
    var JSONItems=[];

        $.getJSON("http://api.fixer.io/"+d, function(data){
       JSONItems = data;

        CCY.push([JSONItems.rates.USD]);
        dts.push([JSONItems.date])   


        });
    } 

    console.log("Date= "+dts);   
    console.log("Rate= "+CCY);