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。

这是根据安迪?

这将执行一个任务，例如每30秒刷新一次页面， 但前提是页面是可见的和集中的。

如果无法检测到可见性，则只使用焦点。

如果用户聚焦页面，那么它将立即更新

页面直到ajax调用后30秒才会再次更新

var windowFocused = true;
var timeOut2 = null;

$(function(){
  $.ajaxSetup ({
    cache: false
  });
  $("#content").ajaxComplete(function(event,request, settings){
       set_refresh_page(); // ajax call has just been made, so page doesn't need updating again for 30 seconds
   });
  // check visibility and focus of window, so as not to keep updating unnecessarily
  (function() {
      var hidden, change, vis = {
              hidden: "visibilitychange",
              mozHidden: "mozvisibilitychange",
              webkitHidden: "webkitvisibilitychange",
              msHidden: "msvisibilitychange",
              oHidden: "ovisibilitychange" /* not currently supported */
          };
      for (hidden in vis) {
          if (vis.hasOwnProperty(hidden) && hidden in document) {
              change = vis[hidden];
              break;
          }
      }
      document.body.className="visible";
      if (change){     // this will check the tab visibility instead of window focus
          document.addEventListener(change, onchange,false);
      }

      if(navigator.appName == "Microsoft Internet Explorer")
         window.onfocus = document.onfocusin = document.onfocusout = onchangeFocus
      else
         window.onfocus = window.onblur = onchangeFocus;

      function onchangeFocus(evt){
        evt = evt || window.event;
        if (evt.type == "focus" || evt.type == "focusin"){
          windowFocused=true; 
        }
        else if (evt.type == "blur" || evt.type == "focusout"){
          windowFocused=false;
        }
        if (evt.type == "focus"){
          update_page();  // only update using window.onfocus, because document.onfocusin can trigger on every click
        }

      }

      function onchange () {
        document.body.className = this[hidden] ? "hidden" : "visible";
        update_page();
      }

      function update_page(){
        if(windowFocused&&(document.body.className=="visible")){
          set_refresh_page(1000);
        }
      }


  })();
  set_refresh_page();
})

function get_date_time_string(){
  var d = new Date();
  var dT = [];
  dT.push(d.getDate());
  dT.push(d.getMonth())
  dT.push(d.getFullYear());
  dT.push(d.getHours());
  dT.push(d.getMinutes());
  dT.push(d.getSeconds());
  dT.push(d.getMilliseconds());
  return dT.join('_');
}

function do_refresh_page(){

// do tasks here

// e.g. some ajax call to update part of the page.

// (date time parameter will probably force the server not to cache)

//      $.ajax({
//        type: "POST",
//        url: "someUrl.php",
//        data: "t=" + get_date_time_string()+"&task=update",
//        success: function(html){
//          $('#content').html(html);
//        }
//      });

}

function set_refresh_page(interval){
  interval = typeof interval !== 'undefined' ? interval : 30000; // default time = 30 seconds
  if(timeOut2 != null) clearTimeout(timeOut2);
  timeOut2 = setTimeout(function(){
    if((document.body.className=="visible")&&windowFocused){
      do_refresh_page();
    }
    set_refresh_page();
  }, interval);
}

我会使用jQuery，因为这样你所要做的就是:

$(window).blur(function(){
  //your code here
});
$(window).focus(function(){
  //your code
});

至少对我有用。

我的代码

let browser_active = ((typeof document.hasFocus != 'undefined' ? document.hasFocus() : 1) ? 1 : 0);
if (!browser_active) {
 // active
} 

我重读了@daniel-buckmaster的版本 我没有做多次尝试，但是，代码对我来说似乎更优雅…

// on-visibility-change.js v1.0.1, based on https://stackoverflow.com/questions/1060008/is-there-a-way-to-detect-if-a-browser-window-is-not-currently-active#38710376
function onVisibilityChange(callback) {
    let d = document;
    let visible = true;
    let prefix;
    if ('hidden' in d) {
        prefix = 'h';
    } else if ('webkitHidden' in d) {
        prefix = 'webkitH';
    } else if ('mozHidden' in d) {
        prefix = 'mozH';
    } else if ('msHidden' in d) {
        prefix = 'msH';
    } else if ('onfocusin' in d) { // ie 9 and lower
        d.onfocusin = focused;
        d.onfocusout = unfocused;
    } else { // others
        window.onpageshow = window.onfocus = focused;
        window.onpagehide = window.onblur = unfocused;
    };
    if (prefix) {
        visible = !d[prefix + 'idden'];
        d.addEventListener(prefix.substring(0, prefix.length - 1) + 'visibilitychange', function() {
            (d[prefix + 'idden'] ? unfocused : focused)();
        });
    };

    function focused() {
        if (!visible) {
            callback(visible = true);
        };
    };

    function unfocused() {
        if (visible) {
            callback(visible = false);
        };
    };
};

使用:页面可见性API

document.addEventListener( 'visibilitychange' , function() {
    if (document.hidden) {
        console.log('bye');
    } else {
        console.log('well back');
    }
}, false );

我能用吗?http://caniuse.com/#feat=pagevisibility