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More about Window and Frame Hierarchies
We've seen a couple of instances of built-in variables being used in the last few examples. One of the built-in variables is window. The window variable refers to whatever window the JavaScript is executing in. If you have some JavaScript in a frame and you write window.document.writeln(), the writeln will happen in that frame. People sometimes
use the built-in variable called self instead of window. The two (window and self) are interchangable.
In the last example, you were introduced to the built-in variable called top. This will always refer to the top-most browser window. If you want to start at the top of the window hierarchy, use top.
Another built-in variable is parent, which refers to the window containing the frame you're currently in. If you have a frameset in a window, and one frame contains another frameset, the second frameset can refer to the enclosing frame using the parent variable. This gets a little tricky so I'm not going to go into it, but here's an example of using JavaScript with frames inside frames for you to look over. Check it out or just go on to your homework for Lesson 3.
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