NEED HELP FAST!! using IndexOf in JavaScript

Hi,
I'm prety new in JS – so hope it's not too basic to the forum.
I'm writing a function (in JavaScript) that getting 2 parameters and searcing if they contain certain strings:

Code (text):

function Example(str1, str2) {

  if (str1.indexOf("aa") > -1)

    str1= "aaa"

  else

    if (str1.indexOf("bb") > -1)

      str1= "bbb"

  if (str2.indexOf("aa") > -1)

    str2= "aaa"

  else

    if (str2.indexOf("bb") > -1)

      str2= "bbb"

  return str1, str2;

}

to test the function – I created ASP.NET…
NEED HELP FAST!! using IndexOf in JavaScript

See original post by Yaeli