JavaScript弹出窗口剧中

javascript的window.open函数弹出窗口，并保持窗口在屏幕上居中显示

function popup(url,name,windowWidth,windowHeight){
    myleft=(screen.width)?(screen.width-windowWidth)/2:100;
	mytop=(screen.height)?(screen.height-windowHeight)/2:100;
	properties = "width="+windowWidth+",height="+windowHeight+",scrollbars=yes, top="+mytop+",left="+myleft;
    window.open(url,name,properties)
}