Professional JavaScript For Web Developers

JavaScript in the Browser
This code creates a frameset with one frame across the top and two frames underneath. Here, the top
frame can be referenced by window.frames[0] or window.frames[“topFrame”], however, you would
probably use the top object instead of window to refer to these frames (making it top.frames[0], for
instance).
The top object always points to the very top (outermost) frame, which is the browser window itself. This
assures that you are pointing to the correct frame. If you then write code within a frame, the window
object referenced in it is a pointer to just that frame.
Because the window object is the center of the BOM universe, it enjoys a special privilege: You don’t
need to explicitly reference it. Whenever a function, object, or collection is referenced, the interpreter
always looks to the window object, so window.frames[0] can be rewritten as just frames[0]. To
understand the various ways to reference the frames in the previous example, refer to Figure 5-4.
Figure 5-4
It is also possible to access a frame directly using its name, such as window.leftFrame. However,
using the frames collection is generally more acceptable because it more accurately represents the
code’s intent.
Another instance of the window object is called parent. The parent object is used with framesets that
load files that are also framesets. Suppose the file named frameset1.htm contains this code:
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