5个不可错过的HTML 5中的API
这次接着介绍5个更多HTML 5的API。这些API还是很实用的。1 fullscreen全屏api,可惜不是全部浏览器支持，播放视频，做游戏时有用
function launchFullScreen(element) {if(element.requestFullScreen) { element.requestFullScreen();} else if(element.mozRequestFullScreen) { element.mozRequestFullScreen();} else if(element.webkitRequestFullScreen) { element.webkitRequestFullScreen();}}// Launch fullscreen for browsers that support it!launchFullScreen(document.documentElement);launchFullScreen(document.getElementById("videoElement")); //点单独的与元素时启动
2 page visiablity页面可见性判断的API
这个可以用来判断当用户的焦点不在当前tab的时候触发，下面这个例子，当CHROME下运行时候，如果新建立一个TAB，并且焦点到了新的tab，则会发现原来的页面的标题的title属性显示为"hidden"了
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";}// Add a listener that constantly changes the titledocument.addEventListener(visibilityChange, function(e) {// Start or stop processing depending on state}, false);
不错的关于这个功能的详细教程：
http://davidwalsh.name/page-visibility
3 getUserMedia api 获得访问媒体设备的API
可以允许调用用户的媒体设备，比如camera等。
window.addEventListener("DOMContentLoaded", function() {// Grab elements, create settings, etc.var canvas = document.getElementById("canvas"), context = canvas.getContext("2d"), video = document.getElementById("video"), videoObj = { "video": true }, errBack = function(error) { console.log("Video capture error: ", error.code); };// 播放if(navigator.getUserMedia) { // Standard navigator.getUserMedia(videoObj, function(stream) { video.src = stream; video.play(); }, errBack);} else if(navigator.webkitGetUserMedia) { // WebKit系列浏览器 navigator.webkitGetUserMedia(videoObj, function(stream){ video.src = window.webkitURL.createObjectURL(stream); video.play(); }, errBack);}}, false);
更具体的教程见：
http://davidwalsh.name/browser-camera
4 电池API
可以获得电池的工作状态
var battery = navigator.battery || navigator.webkitBattery || navigator.mozBattery;console.warn("Battery charging: ", battery.charging); // trueconsole.warn("Battery level: ", battery.level); // 0.58console.warn("Battery discharging time: ", battery.dischargingTime);//电池的监听 battery.addEventListener("chargingchange", function(e) {console.warn("Battery charge change: ", battery.charging);}, false);
这个对移动设备很有效果，相关教程：
http://davidwalsh.name/battery-api
可惜这东西暂时只自mozilla下有效果
5 页面元素预加载 prefetch
主要是浏览器加载完页面后，将其放到浏览器的cache中去，
<link rel="prefetch" href="http://davidwalsh.name/css-enhancements-user-experience" /><link rel="prefetch" href="http://davidwalsh.name/wp-content/themes/walshbook3/images/sprite.png" />
教程：http://davidwalsh.name/html5-prefetch
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