How to Open Outlook with subject and body on change of particular field ServiceNow?

On change Client Script:

function onChange(control, oldValue, newValue, isLoading) {
   if (isLoading || newValue == '') {
      return;
   }
      window.location.href = "mailto:user@example.com?subject=Subject&body=message%20goes%20here";
    //Type appropriate comment here, and begin script below
    }

Image: