Code didn't throw any errors, but employee list fails to display. Is this a problem with how I'm setting up AJAX?

var xhr = new XMLHttpRequest();
xhr.readystatechange = function () {
  if(xhr.readyState === 4) {
    var employees = JSON.parse(xhr.responseText);
    var statusHTML = '<ul class="bulleted">';
    for (var i = 0; i<employees.length; i+=1) {
      if (employees[i].inoffice === true) {
        statusHTML += '<li class = "in">';
      } else {
        statusHTML += '<li class = "out">';
      }
      statusHTML += employees[i].name;
      statusHTML += '</li>';
    }
    statusHTML += '</ul>';
    document.getElementById('employeeList').innerHTML = statusHTML;
  }
};
xhr.open('GET', 'data/employees.json');
xhr.send();