我为我的应用程序创建了一个Comet Chat，当我收到来自我使用的另一个用户的消息时:

if(new_message){
    if(!document.hasFocus()){
        audio.play();
        document.title="Have new messages";
    }
    else{
        audio.stop();
        document.title="Application Name";
    } 
}

简单的/立即检查:

if(document.hidden) {
  // do something
}

可见性变化事件:

document.addEventListener("visibilitychange", function() {
  console.log(document.visibilityState); // "hidden" or "visible"
}, false);

基于承诺的事件:

// An `await`able function that resolves when page visibility changes:
function visibilityChange(state="") {
  return new Promise(resolve => {
    document.addEventListener("visibilitychange", function() {
      if(!state || document.visibilityState === state) { 
        resolve(document.visibilityState);
        document.removeEventListener("visibilitychange", arguments.callee);
      }
    });
  });
}

// Use it like this:
await visibilityChange();
console.log(document.visibilityState);

// Or wait for page to become...
await visibilityChange("visible");
await visibilityChange("hidden");

(注:后两个解是我加到这个答案里的，因为这个问题现在已经结束了，我不能加我自己的答案。以防有人认为我抄袭了那篇文章而没有注明出处。)

对于angular.js，这里有一个指令(基于已接受的答案)，它将允许你的控制器对可见性的变化做出反应:

myApp.directive('reactOnWindowFocus', function($parse) {
    return {
        restrict: "A",
        link: function(scope, element, attrs) {
            var hidden = "hidden";
            var currentlyVisible = true;
            var functionOrExpression = $parse(attrs.reactOnWindowFocus);

          // Standards:
          if (hidden in document)
            document.addEventListener("visibilitychange", onchange);
          else if ((hidden = "mozHidden") in document)
            document.addEventListener("mozvisibilitychange", onchange);
          else if ((hidden = "webkitHidden") in document)
            document.addEventListener("webkitvisibilitychange", onchange);
          else if ((hidden = "msHidden") in document)
            document.addEventListener("msvisibilitychange", onchange);
          else if ("onfocusin" in document) {
                // IE 9 and lower:
            document.onfocusin = onshow;
                document.onfocusout = onhide;
          } else {
                // All others:
            window.onpageshow = window.onfocus = onshow;
                window.onpagehide = window.onblur = onhide;
            }

          function onchange (evt) {
                //occurs both on leaving and on returning
                currentlyVisible = !currentlyVisible;
                doSomethingIfAppropriate();
          }

            function onshow(evt) {
                //for older browsers
                currentlyVisible = true;
                doSomethingIfAppropriate();
            }

            function onhide(evt) {
                //for older browsers
                currentlyVisible = false;
                doSomethingIfAppropriate();
            }

            function doSomethingIfAppropriate() {
                if (currentlyVisible) {
                    //trigger angular digest cycle in this scope
                    scope.$apply(function() {
                        functionOrExpression(scope);
                    });
                }
            }
        }
    };

});

你可以像这样使用它:<div react-on-window-focus="refresh()">，其中refresh()是范围内任何控制器范围内的范围函数。

如果你想对整个浏览器模糊: 正如我所评论的，如果浏览器失去焦点，建议的事件都不会触发。我的想法是在循环中计数，并在事件发生时重置计数器。如果计数器达到限制，我做一个位置。请转到另一页。如果你在开发工具上工作，这也会触发。

var iput=document.getElementById("hiddenInput");
   ,count=1
   ;
function check(){
         count++;
         if(count%2===0){
           iput.focus();
         }
         else{
           iput.blur();
         }
         iput.value=count;  
         if(count>3){
           location.href="http://Nirwana.com";
         }              
         setTimeout(function(){check()},1000);
}   
iput.onblur=function(){count=1}
iput.onfocus=function(){count=1}
check();

这是在FF上成功测试的草稿。

从最初编写这个答案开始，由于W3C，一个新的规范已经达到了推荐状态。页面可见性API(在MDN上)现在允许我们更准确地检测页面何时对用户隐藏。

document.addEventListener("visibilitychange", onchange);

当前浏览器支持:

铬13 + Internet Explorer 10+ Firefox 10 + Opera 12.10+[阅读笔记]

下面的代码在不兼容的浏览器中退回到不太可靠的模糊/聚焦方法:

(function() {
  var hidden = "hidden";

  // Standards:
  if (hidden in document)
    document.addEventListener("visibilitychange", onchange);
  else if ((hidden = "mozHidden") in document)
    document.addEventListener("mozvisibilitychange", onchange);
  else if ((hidden = "webkitHidden") in document)
    document.addEventListener("webkitvisibilitychange", onchange);
  else if ((hidden = "msHidden") in document)
    document.addEventListener("msvisibilitychange", onchange);
  // IE 9 and lower:
  else if ("onfocusin" in document)
    document.onfocusin = document.onfocusout = onchange;
  // All others:
  else
    window.onpageshow = window.onpagehide
    = window.onfocus = window.onblur = onchange;

  function onchange (evt) {
    var v = "visible", h = "hidden",
        evtMap = {
          focus:v, focusin:v, pageshow:v, blur:h, focusout:h, pagehide:h
        };

    evt = evt || window.event;
    if (evt.type in evtMap)
      document.body.className = evtMap[evt.type];
    else
      document.body.className = this[hidden] ? "hidden" : "visible";
  }

  // set the initial state (but only if browser supports the Page Visibility API)
  if( document[hidden] !== undefined )
    onchange({type: document[hidden] ? "blur" : "focus"});
})();

ie9及以下版本需要onfocusin和onfocusout，而所有其他都使用onfocus和onblur，除了iOS，它使用onpageshow和onpagehide。

对于没有jQuery的解决方案，请参阅Visibility.js，它提供了关于三个页面状态的信息

visible    ... page is visible
hidden     ... page is not visible
prerender  ... page is being prerendered by the browser

以及setInterval的方便包装器

/* Perform action every second if visible */
Visibility.every(1000, function () {
    action();
});

/* Perform action every second if visible, every 60 sec if not visible */
Visibility.every(1000, 60*1000, function () {
    action();
});

旧版浏览器(IE < 10;iOS < 7)也可用