How can i format my regular expression which accepts only a valid email format only

 var emailReg = /^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/; 

This is my regular expression . it accepts the email such as

 name.name_@__domain.in

How can i format my regular expression which accepts only a valid email format only. I need the email validation for above example.it is not a duplicate one.