Javascript Comparison

<script language="JavaScript">
function compareValues(value1, value2, value3)
{
	var maxValue;
	if (value1 > value2)
	{
		maxValue = value1;
	}
	else
	{
		maxValue = value2;
	}

	if (maxValue == value3)
	{
		alert("Max value equals value3");
	}
	else
	{
		alert("Max value doesn't equal value3");
	}
}
</script>
value1: <input type="text" name="field1"><br>
value2: <input type="text" name="field2"><br>
value3: <input type="text" name="field3"><br>
<input type="button" name="button" value="Compare" onClick="javascript:compareValues(field1.value, field2.value, field3.value);">
</form>