Check textbox for email format : javascript

-- Check html/ jsp textbox for email address format  --

//Use this function in javascript.

//Call the function @ textbox onChange event

function checkemail(email,errorMail)

      {          

            var testresults;

            var str=document.getElementById(email).value;

            var filter=/^.+@.+\..{2,3}$/;

            if (filter.test(str)){

                 document.getElementById(errorMail).style.display="none";

                 testresults=true;

            }

            else

            {    

                  document.getElementById(errorMail).style.display="block";

                  testresults=false;

            }

            return testresults;

}