How to validate the email address using javascript

var efmt=/^\w+((-\w+)|(\.\w+))*\@[A-Za-z0-9]+((\.|-)[A-Za-z0-9]+)*\.[A-Za-z0-9]+$/;

function EmailFormat(obj)
{
var ctrl=document.getElementById(obj.id);
if((!efmt.test(ctrl.value)) && ctrl.value!='')
{
alert('Please enter a valid email address, like xyz@example.com');
ctrl.value = "";
ctrl.focus();
}
}