// ---------------------------------------------- 
// StyleSwitcher functions written by Paul Sowden 
// http://www.idontsmoke.co.uk/ss/ 
// - - - - - - - - - - - - - - - - - - - - - - - 
// For the details, visit ALA: 
// http://www.alistapart.com/stories/alternate/ 
  
function setActiveStyleSheet(title) {    //根据传递的指定 title，设置样式可用 
    var i, a, main; 
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) { 
        if (a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title")) { 
            a.disabled = true; 
            if (a.getAttribute("title") == title) a.disabled = false; 
        } 
    } 
} 
  
function getActiveStyleSheet() {    //获取当前使用样式的 title 
    var i, a; 
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) { 
        if (a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("title") && !a.disabled) return a.getAttribute("title"); 
    } 
    return null; 
} 
  
function getPreferredStyleSheet() {    //获取预定义/备选样式 
    var i, a; 
    for (i = 0; (a = document.getElementsByTagName("link")[i]); i++) { 
        if (a.getAttribute("rel").indexOf("style") != -1 && a.getAttribute("rel").indexOf("alt") == -1 && a.getAttribute("title")) return a.getAttribute("title"); 
    } 
    return null; 
} 
  
function createCookie(name, value, days) {    //创建 Cookie 
    if (days) { 
        var date = new Date(); 
        date.setTime(date.getTime() + (days * 24 * 60 * 60 * 1000)); 
        var expires = "; expires=" + date.toGMTString(); 
    } 
    else expires = ""; 
    document.cookie = name + "=" + value + expires + "; path=/"; 
} 
  
function readCookie(name) {    //获取指定 Cookie 
    var nameEQ = name + "="; 
    var ca = document.cookie.split(';'); 
    for(var i = 0; i < ca.length; i++) { 
        var c = ca[i]; 
        while (c.charAt(0) == ' ') c = c.substring(1, c.length); 
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length, c.length); 
    } 
    return null; 
} 
  
window.onload = function(e) {    //窗口加载时，调用 Cookie 记录的样式 
    var cookie = readCookie("style"); 
    var title = cookie ? cookie : getPreferredStyleSheet(); 
    setActiveStyleSheet(title); 
} 
  
window.onunload = function(e) { 
    var title = getActiveStyleSheet(); 
    createCookie("style", title, 365); 
} 
  
var cookie = readCookie("style"); 
var title = cookie ? cookie : getPreferredStyleSheet(); 
setActiveStyleSheet(title);