jQuery中getJSON跨域原理的深入讲解

somefunc({“shorturl”: “http:\/\/to.ly\/3XHP”, “ok”: true})

(function() {
 var cross = {
 //设置一个随机的callback函数..防止跟其他的全局函数重名
 callback : 'cross' + parseInt(Math.random()*1000),
 init : function() {
 this.getJSON('http://to.ly/api.php?json=1&longurl='+encodeURIComponent('http://www.skiyo.cn/'), function(data){
 alert(data.shorturl);
 });
 },
 getJSON : function(url, callback) {
 var c = this.callback;
 url = url + "&callback=" + c;
 // Handle JSONP-style loading
 //将函数名设置为window的一个方法,这样此方法就是全局的了.
 window[ c ] = window[ c ] || function( data ) {
 //调用匿名函数
 callback(data);
 // Garbage collect
 window[ c ] = undefined;
 try {
  delete window[ c ];
 } catch(e) {}
 if ( head ) {
  head.removeChild( script );
 }
 };
 var head = document.getElementsByTagName("head")[0] || document.documentElement;
 var script = document.createElement("script");
 script.src = url;
 // Handle Script loading
 var done = false;
 // Attach handlers for all browsers
 script.onload = script.onreadystatechange = function() {
 if ( !done && (!this.readyState 
  this.readyState === "loaded" || this.readyState === "complete") ) {
  done = true;
  // Handle memory leak in IE
  script.onload = script.onreadystatechange = null;
  if ( head && script.parentNode ) {
  head.removeChild( script );
  }
 }
 };
 head.insertBefore( script, head.firstChild );
 },
 };
 //go
 cross.init();
})();