gistfile1.js

$.ajax({
  url: '/path/to/file',
  type: 'POST',
  dataType: 'json',
  data: {param1: 'value1'},
  complete: function(xhr, textStatus) {
    doSomethingOnComplete();
  },
  success: function(data, textStatus, xhr) {
    doSomethingOnSuccess();
  },
  error: function(xhr, textStatus, errorThrown) {
    doSomethingOnError();
  }
});