length in JavaScript

<script language="JavaScript">
    <!--
    var myString1 = new String("Hello, World");

    var myString2 = new String("Here is a longer string");

    var myString3 = new String("Here is an even longer string");

    document.write(myString1 + ": is " + myString1.length);
    document.write(" characters long.<br>");
    document.write(myString2 + ": is " + myString2.length);
    document.write(" characters long.<br>");
    document.write(myString3 + ": is " + myString3.length);
    document.write(" characters long.<br>");
    document.close();
    -->

    </script>