Permutter deux champs d'un formulaire

<form method="get" onSubmit="return validateAddresses(this)" name="formAddresses" action="scripts/interface.mumoro.js" >
	      <tr>
	      <label for="lblstart">Start location : <tinyText>Example: 23 rue de la Chalotais 35000 Rennes France</tinyText></label>
	      <br><tab>
	      <input type="text" name="startAdr" id="startAdr" tabindex="10" size=65 />
	      <input type="button" value="Reverse" onClick="return reverseLocations(this)" />
	      <br>
	      <tab>
	      <label for="lblend">Destination  : </label><br><tab>
	      <input type="text" name="endAdr" id="endAdr" tabindex="20" size=65 /><tab>
          <input type="submit" value="Calculate route" /><span id="formError"></span><br><br>
      </form>

function reverseLocations(f)
{
	var tmp = f.startAdr.value;
	f.startAdr.value = f.endAdr.value;
	f.endAdr.value = tmp;
	return true;
}

function reverseLocations(f)
{
	var tmp = document.getElementById("startAdr").value;
	document.getElementById("startAdr").value = document.getElementById("endAdr").value;
	document.getElementById("endAdr").value = tmp;
	return true;
}

<input type="button" value="Reverse" onClick="return reverseLocations(this.form)">