javascript读写Cookie

function setCookie( sName, sValue, nDays ) {
 var expires = "";
 if ( nDays ) {
  var d = new Date();
  d.setTime( d.getTime() + nDays * 24 * 60 * 60 * 1000 );
  expires = "; expires=" + d.toGMTString();
 }
 document.cookie = sName + "=" + sValue + expires + "; path=/";
};
function getCookie(sName) {
 var re = new RegExp( "(\;|^)[^;]*(" + sName + ")\=([^;]*)(;|$)" );
 var res = re.exec( document.cookie );
 return res != null ? res[3] : null;
};
function removeCookie( name ) {
 setCookie( name, "", -1 );
};