$document.ready(function(){
  $.getJSON('urlThatReturnsAJsonPFileWithCallback=?AppendedToIt', callBackFunction);

  function callBackFunction(json){
  console.log(json.firstProperty);
  }

})

var request = new XMLHttpRequest();
request.open('GET', 'urlThatReturnsJSONFile', true);

request.onload = function() {
  if (request.status >= 200 && request.status < 400) {
    // Success!
    var data = JSON.parse(request.responseText);
    callBackFunction(data);
  }
};
function callBackFunction(json){
  console.log(json.firstProperty);
}
request.send();