As we'll see later in this book, client-side JavaScript has quite a few built-in arrays. For example, the elements[] array of the Form object contains references to the buttons, input fields, and other input elements of an HTML form in a web document. JavaScript provides a length property for these built-in arrays in both Navigator 2.0 and Navigator 3.0. It is only user-defined arrays that lack the length property in Navigator 2.0.
Certain built-in arrays may also have special behavior. For example, in Navigator 3.0, the options[] array of the Select object (an HTML form element) allows you to delete an element simply by setting it to null. This is special-case behavior implemented only for this particular array, and is not a general property of arrays. This kind of behavior is documented on a case-by-case basis in this book.
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