isFollowing Bookmarklet – Who is following who?

isFollowing.js

javascript:(function(){
		/*@author Pablo Cantero - http://pablocantero.com/blog/2010/12/20/isfollowing-bookmarklet-who-is-following-who*/
		var isFollowing = function(twitterScreenNameA, twitterScreenNameB){
			jQuery.getJSON('http://twitter.com/statuses/followers.json?screen_name=' + twitterScreenNameA + '&callback=?', function(data){
				for(var i = 0; i < data.length; i++){
					if(data[i].screen_name === twitterScreenNameB.replace('@', '')){
						alert(twitterScreenNameB + ' is following ' + twitterScreenNameA);
						return;
					}
				}
				alert(twitterScreenNameB + ' is not following ' + twitterScreenNameA);
			});
		};
		var isFollowingPrompt = function(){
			var twitterScreenNameA = window.prompt('input the twitter screen name (a)', jQuery('.screen-name').text());
			var twitterScreenNameB = window.prompt('input the twitter screen name (b)');
			if(twitterScreenNameA === null || twitterScreenNameB === null){
				alert('you must provide the screen names (a) and (b)');
			} else {
				isFollowing(twitterScreenNameA, twitterScreenNameB);
				isFollowing(twitterScreenNameB, twitterScreenNameA);
			}
		};
		if(typeof jQuery === 'undefined') {
			var jQueryScript = document.createElement('script');
			jQueryScript.setAttribute('src','http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.js');
			jQueryScript.setAttribute('type','text/javascript');
			jQueryScript.onreadystatechange= function () {
		      if (this.readyState === 'complete' || this.readyState === 'loaded'){ 
				isFollowingPrompt();
			  }
		   	};
			document.getElementsByTagName('head')[0].appendChild(jQueryScript);
		} else {
			isFollowingPrompt();
		}
})()

How to use it?

Check out this post to get a more detailed explanation
http://pablocantero.com/blog/2010/12/20/isfollowing-bookmarklet-who-is-following-who