Edit in JSFiddle

$("#click").click(function (e) {
 var emailReg = /^([a-zA-Z0-9_\.\-\+])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;;
  if( !emailReg.test( $("#email").val() ) ) {
    alert("Invalid email id");  
    return false;
  } else {
    alert("Valid email id");  
    return true;
  }    
});

<input type="text" id="email"></input> 
<input type="button" value="test" id="click"/>