关于js前端全屏事件

有一个pad端需求，要求进到项目之后在浏览器中将整个项目全屏，

    window.onload = () => {
        let element = document.documentElement
        if (element.requestFullscreen) {
                element.requestFullscreen()
            } else if (element.msRequestFullscreen) { // 兼容ie
                element.msRequestFullscreen()
            } else if (element.mozRequestFullScreen) { // 兼容火狐
                element.mozRequestFullScreen()
            } else if (element.webkitRequestFullscreen) { // 兼容chrome和safari
                element.webkitRequestFullscreen()
            }
        }
    }

是在main.js中写的script标签中实现的

会报错，Failed to execute ‘requestFullscreen’ on ‘Element’: API can only be initiated by a user gesture.
原因在于需要用户点击按钮触发事件，不允许onload触发，会用安全性问题。
可能本来这个需求也有点扯淡

　通过判断元素的requestFullscreen函数是否存在与document.fullscreenEnabled是否为True判断浏览器是否支持全屏或启用全屏，兼容写法为

    function supportfull(){
         var requestFullscreen =
             document.body.requestFullscreen ||
             document.body.webkitRequestFullscreen ||
             document.body.mozRequestFullScreen ||
             document.body.msRequestFullscreen;
         var fullscreenEnabled =
             document.fullscreenEnabled ||
             document.mozFullScreenEnabled ||
             document.webkitFullscreenEnabled ||
             document.msFullscreenEnabled;
         return !!(requestFullscreen && fullscreenEnabled);
     }

判断当前是否全屏

通过document.fullscreenElement属性是否为空来判断，对于webkit内核的浏览器，还可以通过document.webkitIsFullScreen属性来判断，以下为兼容写法

function isfull() {
    return !!(document.webkitIsFullScreen || fullele());
}

退出全屏

　通过document.exitFullscreen方法来退出全屏，对于不同内核的浏览器，方法名除了前缀不一样外，其他地方也不一样，以下为兼容写法

function exitfull() {
    if (document.exitFullscreen) {
        document.exitFullscreen();
    }
    else if (document.mozCancelFullScreen) {
        document.mozCancelFullScreen();
    }
    else if (document.webkitExitFullscreen) {
        document.webkitExitFullscreen();
    }
    else if (document.msExitFullscreen) {
        document.msExitFullscreen();
    }
}