JavaScript: The Definitive Guide, Fourth Edition

The History Object

The history property of the Window object refers to a History object for the window. The History object was originally designed to model the browsing history of a window as an array of recently visited URLs. This turned out to be a poor design choice, however; for important security and privacy reasons, it is almost never appropriate to give a script access to the list of web sites that the user has previously visited. Thus, the array elements of the History object are never actually accessible to scripts (except when the user has granted permission to a signed script in Netscape 4 and later). The length property of the History object is accessible, but it does not provide any useful information.

Although its array elements are inaccessible, the History object supports three methods (which can be used by normal, unsigned scripts in all browser versions). The back( ) and forward( ) methods move backward or forward in a window’s (or frame’s) browsing history, replacing the currently displayed document with a previously viewed one. This is similar to what happens when the user clicks on the Back and Forward browser buttons. The third method, go( ), takes an integer argument and can skip forward or backward in the history list by multiple pages. Unfortunately, go( ) suffers from bugs in Netscape 2 and 3 and has incompatible behavior in Internet Explorer 3; it is best avoided prior to fourth-generation browsers.

Example 13-6 shows how you might use the ...