HTML5 でのページの可視性の決定 (コード付き)

// 各种浏览器兼容 var hidden, state, visibilityChange; 
if (typeof document.hidden !== "undefined") { 
    hidden = "hidden";
    visibilityChange = "visibilitychange"; 
    state = "visibilityState"; 
} else if (typeof document.mozHidden !== "undefined") { 
    hidden = "mozHidden"; 
    visibilityChange = "mozvisibilitychange";
    state = "mozVisibilityState"; 
} else if (typeof document.msHidden !== "undefined") { 
    hidden = "msHidden"; 
    visibilityChange = "msvisibilitychange";
    state = "msVisibilityState"; 
} else if (typeof document.webkitHidden !== "undefined") { 
    hidden = "webkitHidden"; 
    visibilityChange = "webkitvisibilitychange";
    state = "webkitVisibilityState";
 } 
// 添加监听器，在title里显示状态变化
document.addEventListener(visibilityChange, function() { 
    document.title = document[state]; }, false);
// 初始化 
document.title = document[state];

document.addEventListener("visibilitychange", function() {
  console.log( document.visibilityState );
});

document.addEventListener("msvisibilitychange", function() {
  console.log( document.msVisibilityState);
});

document.addEventListener("mozvisibilitychange", function() {
  console.log( document.mozVisibilityState);
});

document.addEventListener("webkitvisibilitychange", function() {
  console.log( document.webkitVisibilityState);
});