Javascript regex to find a base URL -

i'm going mad regex in js:

var patt1=/^http(s)?:\/\/[a-z0-9-]+(.[a-z0-9-]+)*?(:[0-9]+)?(\/)?$/i; 

if give input string "http://www.eitb.com/servicios/concursos/516522/" regex it's supossed return null, because there "folder" after base url. works in php, not in javascript, in script:

<script type="text/javascript"> var str="http://www.eitb.com/servicios/concursos/516522/";  var patt1=/^http(s)?:\/\/[a-z0-9-]+(.[a-z0-9-]+)*?(:[0-9]+)?(\/)?$/i; document.write(str.match(patt1)); </script> 

it returns

http://www.eitb.com/servicios/concursos/516522/,,/516522,,/  

the question is: why not working? how make work?

the idea implement regex in function null when url passed not in correct format:

http://www.eitb.com/ -> correct http://www.eitb.com/something -> incorrect

thanks

i'm no javascript pro, accustomed perl regexp, i'll give try; . in middle of regexp might need escaped, can map / , jinx whole regexp.

try way:

var patt1=/^http(s)?:\/\/[a-z0-9-]+(\.[a-z0-9-]+)*?(:[0-9]+)?(\/)?$/i;