javascript SocialHistory 检查访问者是否访问过某站点

window.onload=function(){

varsl=newSocialHistory();

alert(sl.doesVisit("www.jb51.net"));

}

如果用户曾经使用过www.jb51.net，那么该函数就会返回真，否则返回假。

其实原理并不复杂，它利用了链接的a:visited伪类的属性。首先在页面上生成一个iframe，并在这个iframe中设置a和a:visited为不同的样式。然后将网站的链接插入到iframe中。浏览器就会根据用户的访问历史，为访问过的链接设置a:visited的样式。最后再获得链接的最终样式，如果是a:visited，就可以认为用户访问过该网站了。具体的实现方式可以参考源代码。

这个脚本主要用于显示社会性书签的图标，可以恰到好处地显示用户所使用的网站。但我担心，这样的做法是不是有盗取用户隐私之嫌？虽然这个方法只能判断用户有无访问特定的网站，并不能无限制地得到所有访问历史。

* Social Limit - Only the social you care about.

* Enables your site to know which social bookmarking badges to display to your

* visitors. It tells you all social sites the user has gone to, or you can

* query for a specific one.

* For example:

* var sl = SocialHistory();

* alert( sl.doesVisit("Digg") ); // Returns true/false, -1 if unknown.

* var listOfVisitedSites = sl.visitedSites();

* var checkedSites = sl.checkedSites();

* If you want to add more sites to check, you can pass that in as a dictionary

* to History:

* var more = { "Humanized": "http://humanized.com",

* "Azarask.in": ["http://azarask.in", "http://azarask.in/blog"]

* };

* var sl = SocialHistory(more);

* alert( sl.doesVisit("Humanized") );

* For a list of built-in sites, see the sites variable below.

* Permission is hereby granted, free of charge, to any person obtaining a copy

* of this software and associated documentation files (the "Software"), to deal

* in the Software without restriction, including without limitation the rights

* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

* copies of the Software, and to permit persons to whom the Software is

* furnished to do so, subject to the following conditions:

* The above copyright notice and this permission notice shall be included in

* all copies or substantial portions of the Software.

* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

* THE SOFTWARE.

var SocialHistory = function( moreSites ){

var sites = {

"Digg": ["http://digg.com", "http://digg.com/login"],

"Reddit": ["http://reddit.com", "http://reddit.com/new/", "http://reddit.com/controversial/", "http://reddit.com/top/", "http://reddit.com/r/reddit.com/", "http://reddit.com/r/programming/"],

"StumbleUpon": ["http://stumbleupon.com"],

"Yahoo Buzz": ["http://buzz.yahoo.com"],

"Facebook": ["http://facebook.com/home.php", "http://facebook.com", "https://login.facebook.com/login.php"],

"Del.icio.us": ["https://secure.del.icio.us/login", "http://del.icio.us/"],

"MySpace": ["http://www.myspace.com/"],

"Technorati": ["http://www.technorati.com"],

"Newsvine": ["https://www.newsvine.com", "https://www.newsvine.com/_tools/user/login"],

"Songza": ["http://songza.com"],

"Slashdot": ["http://slashdot.org/"],

"Ma.gnolia": ["http://ma.gnolia.com/"],

"Blinklist": ["http://www.blinklist.com"],

"Furl": ["http://furl.net", "http://furl.net/members/login"],

"Mister Wong": ["http://www.mister-wong.com"],

"Current": ["http://current.com", "http://current.com/login.html"],

"Menaeme": ["http://meneame.net", "http://meneame.net/login.php"],

"Oknotizie": ["http://oknotizie.alice.it", "http://oknotizie.alice.it/login.html.php"],

"Diigo": ["http://www.diigo.com/", "https://secure.diigo.com/sign-in"],

"Funp": ["http://funp.com", "http://funp.com/account/loginpage.php"],

"Blogmarks": ["http://blogmarks.net"],

"Yahoo Bookmarks": ["http://bookmarks.yahoo.com"],

"Xanga": ["http://xanga.com"],

"Blogger": ["http://blogger.com"],

"Last.fm": ["http://www.last.fm/", "https://www.last.fm/login/"],

"N4G": ["http://www.n4g.com"],

"Faves": ["http://faves.com", "http://faves.com/home", "https://secure.faves.com/signIn"],

"Simpy": ["http://www.simpy.com", "http://www.simpy.com/login"],

"Yigg": ["http://www.yigg.de"],

"Kirtsy": ["http://www.kirtsy.com", "http://www.kirtsy.com/login.php"],

"Fark": ["http://www.fark.com", "http://cgi.fark.com/cgi/fark/users.pl?self=1"],

"Mixx": ["https://www.mixx.com/login/dual", "http://www.mixx.com"],

"Google Bookmarks": ["http://www.google.com/bookmarks", "http://www.google.com/ig/add?moduleurl=bookmarks.xml&hl=en"],

"Subbmitt": ["http://subbmitt.com/"]

};

for( var site in moreSites ) {

// If we don't have the site, create the URL list.

if( typeof( sites[site] ) == "undefined" ) sites[site] = [];

// If the value is string, just push that onto the URL list.

if( typeof( moreSites[site] ) == "string" )

sites[site].push( moreSites[site] );

else

sites[site] = sites[site].concat( moreSites[site] );

}

var visited = {};

function getStyle(el, scopeDoc,styleProp) {

if (el.currentStyle)

var y = el.currentStyle[styleProp];

else if (window.getComputedStyle)

var y = scopeDoc.defaultView.getComputedStyle(el,null).getPropertyValue(styleProp);

return y;

}

function remove( el ) {

el.parentNode.removeChild( el );

}

// Code inspired by:

// bindzus.wordpress.com/2007/12/24/adding-dynamic-contents-to-iframes

function createIframe() {

var iframe = document.createElement("iframe");

iframe.style.position = "absolute";

iframe.style.visibility = "hidden";

document.body.appendChild(iframe);

// Firefox, Opera

if(iframe.contentDocument) iframe.doc = iframe.contentDocument;

// Internet Explorer

else if(iframe.contentWindow) iframe.doc = iframe.contentWindow.document;

// Magic: Force creation of the body (which is null by default in IE).

// Also force the styles of visited/not-visted links.

iframe.doc.open();

iframe.doc.write('<style>');

iframe.doc.write("a{color: #000000; display:none;}");

iframe.doc.write("a:visited {color: #FF0000; display:inline;}");

iframe.doc.write('</style>');

iframe.doc.close();

// Return the iframe: iframe.doc contains the iframe.

return iframe;

}

var iframe = createIframe();

function embedLinkInIframe( href, text ) {

var a = iframe.doc.createElement("a");

a.href = href;

a.innerHTML = site;

iframe.doc.body.appendChild( a );

}

for( var site in sites ) {

var urls = sites[site];

for( var i=0; i<urls.length; i++ ) {

// You have to create elements in the scope of the iframe for IE.

embedLinkInIframe( urls[i], site );

// Automatically try variations of the URLS with and without the "www"

if( urls[i].match(/www./) ){

var sansWWW = urls[i].replace(/www./, "");

embedLinkInIframe( sansWWW, site );

} else {

// 2 = 1 for length of string + 1 for slice offset

var httpLen = urls[i].indexOf("//") + 2;

var withWWW = urls[i].substring(0, httpLen ) + "www." + urls[i].substring( httpLen );

embedLinkInIframe( withWWW, site );

}

var links = iframe.doc.body.childNodes;

for( var i=0; i<links.length; i++) {

// Handle both Firefox/Safari, and IE (respectively)

var displayValue = getStyle(links[i], iframe.doc, "display");

var didVisit = displayValue != "none";

if( didVisit ){

visited[ links[i].innerHTML ] = true;

}

remove( iframe );

return new (function(){

var usedSites = [];

for( var site in visited ){

usedSites.push( site );

}

// Return an array of visited sites.

this.visitedSites = function() {

return usedSites;

}

// Return true/false. If we didn't check the site, return -1.

this.doesVisit = function( site ) {

if( typeof( sites[site] ) == "undefined" )

return -1;

return typeof( visited[site] ) != "undefined";

}

var checkedSites = [];

for( var site in sites ){

checkedSites.push( site );

}

// Return a list of the sites checked.

this.checkedSites = function(){

return checkedSites;

}

})();

}