HTML5全屏瀏覽器兼容方案

最近一個項目有頁面全屏的的需求，搜索了下有HTML5的全屏API可用，不過各瀏覽器的支持不一樣。

標準	webkit	Firefox	IE
Element.requestFullscreen()	webkitRequestFullscreen	mozRequestFullScreen	msRequestFullscreen
Document.exitFullscreen()	webkitExitFullscreen	mozCancelFullScreen	msExitFullscreen
Document.fullscreenElement	webkitFullscreenElement	mozFullScreenElement	msFullscreenElement
Document.fullscreenEnabled	webkitFullscreenEnabled	mozFullScreenEnabled	msFullscreenEnabled
Document.fullscreenchange	webkitfullscreenchange	mozfullscreenchange	MSFullscreenChange
Document.fullscreenerror	webkitfullscreenerror	mozfullscreenerror	MSFullscreenError

MDN Fullscreen API: The Fullscreen API provides an easy way for web content to be presented using the user's entire screen. The API lets you easily direct the browser to make an element and its children, if any, occupy the fullscreen, eliminating all browser user interface and other applications from the screen for the duration.

全屏接口提供了簡單的方式通過用戶整個屏幕展示瀏覽器的內容。這個接口讓我們很輕鬆的引導瀏覽器使一個元素和它的子元素佔據整個屏幕，並且從屏幕上消除所有瀏覽器用戶界面和其它應用程序。

一、接口使用（以谷歌瀏覽器爲例）

1.requestFullscreen()

全屏請求方法，使用方法：Element.requestFullscreen()。

<div id="example">
    <img src="html5.png">
    <button type="button" id="requestFullscreen">requestFullscreen</button>
</div>

<script>
// 全屏
document.getElementById('requestFullscreen').addEventListener('click', () => {
    document.querySelector('img').webkitRequestFullscreen();
});
</script>

觸發事件後會有按ESC即可退出全屏模式的文字提示。

注意

1.在< iframe >框架中使用全屏需要加allowfullscreen屬性。
2.全屏請求只能通過用戶操作觸發，否則會出現Failed to execute 'requestFullscreen' on 'Element': API can only be initiated by a user gesture.這樣的警告，解決辦法是將此方法綁定到某個用戶操作事件上，例如點擊事件click。

(function () {
    document.documentElement.webkitRequestFullscreen();
})();

2.exitFullscreen()

退出全屏模式的方法，使用方法：document.exitFullscreen()，除了requestFullscreen()其它方法和屬性都是基於document的。

<div id="example">
    <img src="html5.png">
    <button type="button" id="requestFullscreen">requestFullscreen</button>
    <button type="button" id="exitFullscreen">exitFullscreen</button>
</div>

<script>
// 退出全屏
document.getElementById('exitFullscreen').addEventListener('click', () => {
    document.webkitExitFullscreen();
});
</script>

觸發後退出全屏恢復頁面原來的樣子，也可以按ESC退出；另外F11也可以使頁面全屏顯示和退出，但這應該屬於瀏覽器的功能，不在HTML5 API的範疇之內。

3.fullscreenElement

若是全屏模式下，顯示全屏的元素，若不是，返回null。

<div id="example">
    <img src="html5.png">
    <button type="button" id="requestFullscreen">requestFullscreen</button>
    <button type="button" id="exitFullscreen">exitFullscreen</button>
    <button type="button" id="fullscreenElement">fullscreenElement</button>
</div>

<script>
// 顯示全屏元素
document.getElementById('fullscreenElement').addEventListener('click', () => {
    console.log(document.webkitFullscreenElement); // <div id=...></div> 或 null
});
</script>

4.fullscreenEnabled

返回一個布爾值true/false，判斷是否可用全屏模式。

<div id="example">
    <img src="html5.png">
    <button type="button" id="fullscreenEnabled">fullscreenEnabled</button>
</div>

<script>
// 全屏是否可用
document.getElementById('fullscreenEnabled').addEventListener('click', () => {
    console.log(document.webkitFullscreenEnabled); // true
});
</script>

二、瀏覽器兼容

由於各主流瀏覽器調用全屏接口的方法不一致，所以調用之前需要判斷一下當前瀏覽器適用的方法。

我簡單的做了下請求全屏和退出全屏的適配。

const MAZEY_FULL_SCREEN = function () {
    let prefixArr = ['', 'webkit', 'moz', 'ms'], // 瀏覽器前綴
        isRightRequest, // 是否找到適配的方法
        isRightExit,
        requestMethod, // 全屏方法
        exitMethod, // 退出全屏方法
        lowerFirst = function (str) {
            return str.slice(0, 1).toLowerCase() + str.slice(1);
        },
        requestSuffixArr = ['RequestFullscreen', 'RequestFullScreen'], // 後綴
        exitSuffixArr = ['ExitFullscreen', 'CancelFullScreen'],
        searchRightMethod = function (prefix, suffixArr, documentParent) {
            let methodArr = suffixArr.map((suffix) => {
                return prefix + suffix;
            }),
            method,
            isRight;
            methodArr.forEach((wholePrefix) => {
                if (isRight) return;
                if (prefix.length === 0) {
                    wholePrefix = lowerFirst(wholePrefix)
                }
                if (wholePrefix in documentParent) {
                    method = wholePrefix;
                    isRight = true;
                    // console.log(method);
                }
            });
            return method;
        };
    prefixArr.forEach((prefix) => {
        if (isRightRequest && isRightExit) return;
        // 查找請求
        requestMethod = searchRightMethod(prefix, requestSuffixArr, document.documentElement);
        isRightRequest = Boolean(requestMethod);
        // 查找退出
        exitMethod = searchRightMethod(prefix, exitSuffixArr, document);
        isRightExit = Boolean(exitMethod);
    });
    this.request = function (element) {
        let domEle = document.querySelector(element) || document.documentElement;
        domEle[requestMethod]();
    };
    this.exit = function () {
        document[exitMethod]();
    };
};

let fullscreen = new MAZEY_FULL_SCREEN();

使用示例：

<h1 id="h1">html5 - 全屏</h1>
<button id="request">請求</button>
<button id="exit">退出</button>
<script src="mazey-full-screen.js"></script>

<script>
// 請求全屏
document.getElementById('request').addEventListener('click', () => {
    fullscreen.request();
});
// 退出全屏
document.getElementById('exit').addEventListener('click', () => {
    fullscreen.exit();
});
</script>

示例代碼：GitHub