我有JavaScript，它周期性地执行活动。当用户没有在看站点时(例如，窗口或选项卡没有焦点)，最好不要运行。
是否有一种方法可以使用JavaScript来做到这一点?
我的参考点:如果你正在使用的窗口不活跃，Gmail聊天就会播放声音。
当前回答
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。
其他回答
我的代码
let browser_active = ((typeof document.hasFocus != 'undefined' ? document.hasFocus() : 1) ? 1 : 0);
if (!browser_active) {
// active
}
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。
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。
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
