function toggleFullScreen() {  
    if (!document.fullscreenElement && // alternative standard method  
        !document.mozFullScreenElement && !document.webkitFullscreenElement) {// current working methods  
        if (document.documentElement.requestFullscreen) {  
            document.documentElement.requestFullscreen();  
        } else if (document.documentElement.mozRequestFullScreen) {  
            document.documentElement.mozRequestFullScreen();  
        } else if (document.documentElement.webkitRequestFullscreen) {  
            document.documentElement.webkitRequestFullscreen(Element.ALLOW_KEYBOARD_INPUT);  
        }  
    } else {  
        if (document.cancelFullScreen) {  
            document.cancelFullScreen();  
        } else if (document.mozCancelFullScreen) {  
            document.mozCancelFullScreen();  
        } else if (document.webkitCancelFullScreen) {  
            document.webkitCancelFullScreen();  
        }  
    }  
}  

1. <input value="全屏" type='button' onclick='toggleFullScreen();' />