SOURCE

//全屏是只某一个盒子为全屏展示，但是不是所有的都可以全屏，比如页面的button就不行，退出全屏是document的事件
var dv = document.querySelector('div')
function launchFullScreen(element) {
    console.log(1132)
    if (dv.requestFullscreen) {
        dv.requestFullscreen()
    } else if (dv.mozRequestFullScreen) {
        dv.mozRequestFullScreen()
    } else if (dv.webkitRequestFullscreen) {
        dv.webkitRequestFullscreen()
    } else if (dv.msRequestFullscreen) {
        dv.msRequestFullscreen()
    }
}
function exitFullscreen() {
    if (document.exitFullscreen) {
        document.exitFullscreen()
    } else if (document.mozCancelFullScreen) {
        document.mozCancelFullScreen()
    } else if (document.webkitExitFullscreen) {
        document.webkitExitFullscreen()
    }
}
btn.addEventListener('click', launchFullScreen)

document.onkeydown = function (event) {
    if (event.keyCode == 13) {
        exitFullscreen()
    }
}

 <button id="btn">点击全屏</button>
<div>1111</div>

div {
    width: 500px;
    height: 500px;
    background-color: pink;
}