Validating (Length and [is numeric] ) Phone Numbers in CRM 2013

hello,
to make sure that your phone field is just contains numbers with fixed length  see this function:
in this example we set the max lenght is 10:

function validatePhone(context)
{
var phone =context.getEventSource().getValue();
var sTmp = phone.replace(/[^0-9]/g, "");
phoneRegex = /^\d{10}$/;
if( !sTmp.match( phoneRegex ) )
   {
   event.returnValue = false;
   alert("Phone must contain 10 numbers.") ;
   }
else
  {
   var sTmpClean =  "(" + sTmp.substr(0, 3) + ") " + sTmp.substr(3, 3) + "-" + sTmp.substr(6, 4);
   context.getEventSource().setValue(sTmpClean);
  }
}