how to post an article by jquery using REST service of Drupal? i want to create an article by rest services of drupal ?
as given in the documentation on Drupal Post docs link

but it gives an error Reference error : Drupal is not defined    

in the following line of code jQuery.get(Drupal.url('rest/session/token'))

here is my code based on docs 

function getCsrfToken(callback) {
  jQuery.get(Drupal.url('rest/session/token'))
    .done(function (data) {
      var csrfToken = data;
      callback(csrfToken);
    });
}


function postNode(csrfToken, node) {
  jQuery.ajax({
    url: 'http://localhost/dr/entity/node?_format=hal_json',
    method: 'POST',
    headers: {
      'Content-Type': 'application/hal+json',
      'X-CSRF-Token': csrfToken

    },
    data: JSON.stringify(node),
    success: function (node) {
      console.log(node);
    }
  });
}

var newNode = {
  _links: {
    type: {
      href: 'http://localhost/dr/rest/type/node/article'
    }
  },
  type: {
    target_id: 'article'
  },
  title: {
    value: 'Example node title'
  }
}; 

getCsrfToken(function (csrfToken) {
  postNode(csrfToken, newNode);
});
You need to enclose your javascript

(function ($, Drupal) {

  ...

})(jQuery, Drupal);


to access Drupal and the usual $ for jQuery.