Google App script: toString() with formating

I like to output a number based on a format. Looks like string.format is not supported in Google App script. May I know what options do I have? Here is a sample code to explain my need.

function test(){
  var r=1/3;
  var st=r.toString();
  Logger.log(st.Format("0.00"));  // I like to see 3.33 instead of 3.333333333