检测浏览器选项卡是否具有焦点

是否有可靠的跨浏览器方式来检测选项卡是否具有焦点。

情况是，我们有一个应用程序定期轮询股票价格，如果页面没有重点关注，我们可以停止轮询并为每个人节省交通噪音，尤其是当人们热衷于打开具有不同投资组合的多个标签时。

是window.onblur并且window.onfocus为此选择吗？

是的，window.onfocus并且window.onblur应该适合您的方案：

http://www.thefutureoftheweb.com/blog/detect-browser-window-focus

重要编辑：这个答案已经过时。自编写以来，就引入了Visibility API（ mdn， example， spec）。这是解决此问题的更好方法。

var focused = true;

window.onfocus = function() {
    focused = true;
};
window.onblur = function() {
    focused = false;
};

AFAIK，focus并blur在所有方面均受支持。（请参阅http://www.quirksmode.org/dom/events/index.html）

在搜索此问题时，我发现应该使用Page Visibility API的建议。大多数现代浏览器根据“我可以使用”来支持此API：http : //caniuse.com/#feat=pagevisibility。

这是一个工作示例（来自此片段）：

$(document).ready(function() {
  var hidden, visibilityState, visibilityChange;

  if (typeof document.hidden !== "undefined") {
    hidden = "hidden", visibilityChange = "visibilitychange", visibilityState = "visibilityState";
  } else if (typeof document.msHidden !== "undefined") {
    hidden = "msHidden", visibilityChange = "msvisibilitychange", visibilityState = "msVisibilityState";
  }

  var document_hidden = document[hidden];

  document.addEventListener(visibilityChange, function() {
    if(document_hidden != document[hidden]) {
      if(document[hidden]) {
        // Document hidden
      } else {
        // Document shown
      }

      document_hidden = document[hidden];
    }
  });
});

更新：上面的示例曾经为Gecko和WebKit浏览器提供了前缀属性，但是我删除了该实现，因为一段时间以来这些浏览器一直在提供没有前缀的Page Visibility API。为了保留与IE10的兼容性，我保留了Microsoft特定的前缀。

惊讶地看到没人提及 document.hasFocus

if (document.hasFocus()) console.log('Tab is active')

MDN有更多信息。

是的，这些应该为您工作。您只是让我想起了我遇到的利用这些技术的链接。有趣的读物

我会这样做（参考http://www.w3.org/TR/page-visibility/）：

    window.onload = function() {

        // check the visiblility of the page
        var hidden, visibilityState, visibilityChange;

        if (typeof document.hidden !== "undefined") {
            hidden = "hidden", visibilityChange = "visibilitychange", visibilityState = "visibilityState";
        }
        else if (typeof document.mozHidden !== "undefined") {
            hidden = "mozHidden", visibilityChange = "mozvisibilitychange", visibilityState = "mozVisibilityState";
        }
        else if (typeof document.msHidden !== "undefined") {
            hidden = "msHidden", visibilityChange = "msvisibilitychange", visibilityState = "msVisibilityState";
        }
        else if (typeof document.webkitHidden !== "undefined") {
            hidden = "webkitHidden", visibilityChange = "webkitvisibilitychange", visibilityState = "webkitVisibilityState";
        }


        if (typeof document.addEventListener === "undefined" || typeof hidden === "undefined") {
            // not supported
        }
        else {
            document.addEventListener(visibilityChange, function() {
                console.log("hidden: " + document[hidden]);
                console.log(document[visibilityState]);

                switch (document[visibilityState]) {
                case "visible":
                    // visible
                    break;
                case "hidden":
                    // hidden
                    break;
                }
            }, false);
        }

        if (document[visibilityState] === "visible") {
            // visible
        }

    };  

跨浏览器jQuery解决方案！ _{原始可从GitHub获得}

有趣且易于使用！

以下插件将通过IE，Chrome，Firefox，Safari等各种版本的标准测试。并相应地建立声明的方法。它还处理以下问题：

• onblur | .blur / onfocus | .focus“ 重复 ”调用
• 通过选择替代应用程序（例如word），窗口失去了焦点
• • 这往往是不受欢迎的，因为，如果您打开了银行页面，并且onblur事件告诉它屏蔽了该页面，那么如果您打开计算器，您将无法再看到该页面！
• 没有在页面加载时触发

使用非常简单：_{向下滚动到“ 运行代码段 ”}

$.winFocus(function(event, isVisible) {
    console.log("Combo\t\t", event, isVisible);
});

//  OR Pass False boolean, and it will not trigger on load,
//  Instead, it will first trigger on first blur of current tab_window
$.winFocus(function(event, isVisible) {
    console.log("Combo\t\t", event, isVisible);
}, false);

//  OR Establish an object having methods "blur" & "focus", and/or "blurFocus"
//  (yes, you can set all 3, tho blurFocus is the only one with an 'isVisible' param)
$.winFocus({
    blur: function(event) {
        console.log("Blur\t\t", event);
    },
    focus: function(event) {
        console.log("Focus\t\t", event);
    }
});

//  OR First method becoms a "blur", second method becoms "focus"!
$.winFocus(function(event) {
    console.log("Blur\t\t", event);
},
function(event) {
    console.log("Focus\t\t", event);
});

/*    Begin Plugin    */
;;(function($){$.winFocus||($.extend({winFocus:function(){var a=!0,b=[];$(document).data("winFocus")||$(document).data("winFocus",$.winFocus.init());for(x in arguments)"object"==typeof arguments[x]?(arguments[x].blur&&$.winFocus.methods.blur.push(arguments[x].blur),arguments[x].focus&&$.winFocus.methods.focus.push(arguments[x].focus),arguments[x].blurFocus&&$.winFocus.methods.blurFocus.push(arguments[x].blurFocus),arguments[x].initRun&&(a=arguments[x].initRun)):"function"==typeof arguments[x]?b.push(arguments[x]):
"boolean"==typeof arguments[x]&&(a=arguments[x]);b&&(1==b.length?$.winFocus.methods.blurFocus.push(b[0]):($.winFocus.methods.blur.push(b[0]),$.winFocus.methods.focus.push(b[1])));if(a)$.winFocus.methods.onChange()}}),$.winFocus.init=function(){$.winFocus.props.hidden in document?document.addEventListener("visibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="mozHidden")in document?document.addEventListener("mozvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden=
"webkitHidden")in document?document.addEventListener("webkitvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="msHidden")in document?document.addEventListener("msvisibilitychange",$.winFocus.methods.onChange):($.winFocus.props.hidden="onfocusin")in document?document.onfocusin=document.onfocusout=$.winFocus.methods.onChange:window.onpageshow=window.onpagehide=window.onfocus=window.onblur=$.winFocus.methods.onChange;return $.winFocus},$.winFocus.methods={blurFocus:[],blur:[],focus:[],
exeCB:function(a){$.winFocus.methods.blurFocus&&$.each($.winFocus.methods.blurFocus,function(b,c){this.apply($.winFocus,[a,!a.hidden])});a.hidden&&$.winFocus.methods.blur&&$.each($.winFocus.methods.blur,function(b,c){this.apply($.winFocus,[a])});!a.hidden&&$.winFocus.methods.focus&&$.each($.winFocus.methods.focus,function(b,c){this.apply($.winFocus,[a])})},onChange:function(a){var b={focus:!1,focusin:!1,pageshow:!1,blur:!0,focusout:!0,pagehide:!0};if(a=a||window.event)a.hidden=a.type in b?b[a.type]:
document[$.winFocus.props.hidden],$(window).data("visible",!a.hidden),$.winFocus.methods.exeCB(a);else try{$.winFocus.methods.onChange.call(document,new Event("visibilitychange"))}catch(c){}}},$.winFocus.props={hidden:"hidden"})})(jQuery);
/*    End Plugin      */

// Simple example
$(function() {
	$.winFocus(function(event, isVisible) {
		$('td tbody').empty();
		$.each(event, function(i) {
			$('td tbody').append(
				$('<tr />').append(
					$('<th />', { text: i }),
					$('<td />', { text: this.toString() })
				)
			)
		});
		if (isVisible) 
			$("#isVisible").stop().delay(100).fadeOut('fast', function(e) {
				$('body').addClass('visible');
				$(this).stop().text('TRUE').fadeIn('slow');
			});
		else {
			$('body').removeClass('visible');
			$("#isVisible").text('FALSE');
		}
	});
})

body { background: #AAF; }
table { width: 100%; }
table table { border-collapse: collapse; margin: 0 auto; width: auto; }
tbody > tr > th { text-align: right; }
td { width: 50%; }
th, td { padding: .1em .5em; }
td th, td td { border: 1px solid; }
.visible { background: #FFA; }

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<h3>See Console for Event Object Returned</h3>
<table>
    <tr>
        <th><p>Is Visible?</p></th>
        <td><p id="isVisible">TRUE</p></td>
    </tr>
    <tr>
        <td colspan="2">
            <table>
                <thead>
                    <tr>
                        <th colspan="2">Event Data <span style="font-size: .8em;">{ See Console for More Details }</span></th>
                    </tr>
                </thead>
                <tbody></tbody>
            </table>
        </td>
    </tr>
</table>