js 動的にstylesheetを書きかえる

忘れてたので忘れないようにメモ

    var oSheet =  document.styleSheets[0];
    var oRule = oSheet.rules || oSheet.cssRules;
    var iWidth=oRule[2].style.width.replace("px","");
    var iHeight=oRule[2].style.height.replace("px","");
    oRule[2].style.width=( iWidth * 2 / 3 ) + "px"; 
    oRule[2].style.height=( iHeight * 2 / 3 ) + "px";