<a id="mylink" href="http://mysite.com">Щелкни</a><br>

<script>
  function $(id){
    return document.getElementById(id)
  }

  url = document.links.mylink.href
  document.write('URL-адрес — ' + url)

  url = $('mylink').href
  document.write('URL-адрес — ' + url)

  url = document.links.mylink.href
  document.write('URL-адрес — ' + url)
</script>