get cross-domain data without jquery

define a callback function

<script type='text/javascript'>
  
  var num;
  function getdata1(content) {
     num=content;
     alert("data taken from external site: num="+num);
  }
</script>

http://file.madisk.com/getdata1.js

 getdata1("123");

load data

 <script type="text/javascript"
         src="http://file.madisk.com/getdata1.js">
 </script>