JSONP or JSON-P (JSON with Padding)

JSONP, or JSON-P (JSON with Padding), is a historical JavaScript technique for requesting data by loading a <script> element, which is an element intended to load ordinary JavaScript.

json-p.org
en.wikipedia.org/wiki/JSONP

Usage

var script = document.createElement('script'); 
script.src = 'http://server.example.com/Users/1234?callback=parseResponse';
document.getElementsByTagName('head')[0].appendChild(script); 

function parseResponse(data){ 
  //callback method 
}
  

$.ajax({
  url: 'http://server.example.com/Users/1234',
  dataType: 'jsonp',
  jsonpCallback: "parseResponse",
  success: callback
});
  