js实现全屏和退出全屏功能

主要是全屏和退出全屏事件，以及相应的操作（采用window.onresize监测）

$(function(){
    
    
    //全屏
    $("#fullScreen").on("click",function(){
    
    
        fullScreen();
    })
    //退出全屏
    $("#exitFullScreen").on("click",function(){
    
    
        exitFullscreen();
    })
})

//fullScreen()和exitScreen()有多种实现方式，此处只使用了其中一种
//全屏
function fullScreen() {
    
    
    var element = document.documentElement;
    if (element.requestFullscreen) {
    
    
        element.requestFullscreen();
    } else if (element.msRequestFullscreen) {
    
    
        element.msRequestFullscreen();
    } else if (element.mozRequestFullScreen) {
    
    
        element.mozRequestFullScreen();
    } else if (element.webkitRequestFullscreen) {
    
    
        element.webkitRequestFullscreen();
    }
}

//退出全屏 
function exitFullscreen() {
    
    
    if (document.exitFullscreen) {
    
    
        document.exitFullscreen();
    } else if (document.msExitFullscreen) {
    
    
        document.msExitFullscreen();
    } else if (document.mozCancelFullScreen) {
    
    
        document.mozCancelFullScreen();
    } else if (document.webkitExitFullscreen) {
    
    
        document.webkitExitFullscreen();
    }
}

//监听window是否全屏，并进行相应的操作,支持esc键退出
window.onresize = function() {
    
    
    var isFull=!!(document.webkitIsFullScreen || document.mozFullScreen || 
        document.msFullscreenElement || document.fullscreenElement
    );//!document.webkitIsFullScreen都为true。因此用!!
    if (isFull==false) {
    
    
        $("#exitFullScreen").css("display","none");
        $("#fullScreen").css("display","");
    }else{
    
    
        $("#exitFullScreen").css("display","");
        $("#fullScreen").css("display","none");
    }
}

补充：
!和!!的区别
! 变量转换成boolean类型判断，null、undefined和空字符串取反都为false，其余都为true。
!! 用来做类型判断
if(a!=null&&typeof(a)!=undefined&&a!=’’){}
等价于if(!!a){}