Mutual references between frames

All frames in a page are provided in the form of a collection as attributes of the window object. For example: window.frames represents the collection of all frames in the page, which is the same as the form object , link objects, picture objects, etc. are similar, but the difference is that these collections are attributes of the document. Therefore, to reference a subframe, you can use the following syntax:

Among them, the word window can also be replaced or omitted with self. Assuming that frameName is the first frame in the page, the following writing methods are equivalent:

Each frame corresponds to an HTML page, so this frame is also an independent browser window. It has all the properties of a window. The so-called reference to the frame is also a reference to the window object. With this window object, you can easily operate the pages in it, such as using the window.document object to write data to the page, using the window.location property to change the page in the frame, etc.
The following introduces the mutual references between different levels of frameworks:

1． Reference from parent frame to child frame
Knowing the above principles, it is very easy to reference the child frame from the parent frame, that is:

This references the subframe named frameName within the page. If you want to reference a subframe within a subframe, according to the nature of the referenced frame, which is actually the window object, you can implement it like this:

In this way, the second-level sub-frame is referenced, and so on. , can realize the reference of multi-layer framework.

2． Reference from child frame to parent frame
Each window object has a parent attribute that represents its parent frame. If the frame is already a top-level frame, window.parent also represents the frame itself.

3． References between sibling frames
If two frames are sub-frames of the same frame, they are called sibling frames and can reference each other through the parent frame. For example, a page includes 2 sub-frames:

You can use the following statement in frame1 to reference frame2:

4． Mutual references between different levels of frameworks
The level of the framework is for the top-level framework. When the levels are different, as long as you know the level you are at and the level and name of the other frame, you can easily access each other by using the properties of the window object referenced by the frame, for example:

5． The reference to the top-level frame
is similar to the parent attribute. The window object also has a top attribute. It represents a reference to the top-level frame, which can be used to determine whether a frame itself is a top-level frame, for example:

Change the loading page of the frame
The reference to the frame is the reference to the window object. Using the location attribute of the window object, you can change the navigation of the frame, for example:
window.frames[0].location= "1.html";
This will redirect the page of the first frame in the page to 1.html. Using this property, you can even use one link to update multiple frames.

Referencing JavaScript variables and functions in other frameworks
Before introducing the technique of referencing JavaScript variables and functions in other frameworks, let’s take a look at the following code:

If you run this code, a "hello, ajax!" window will pop up, which is the result of executing the hello() function. So why did hello() become a method of the window object? Because all global variables and global functions defined within a page are members of the window object. For example:

will pop up a dialog box showing 1. The same principle applies to sharing variables and functions between different frameworks by calling them through the window object.
For example: a product browsing page consists of two sub-frames. The left side represents the link of the product category; when the user clicks the category link, the corresponding product list is displayed on the right side; the user can click the [Purchase] link next to the product Add items to cart.
In this example, you can use the left navigation page to store the products that the user wants to buy, because when the user clicks the navigation link, what changes is another page, the product display page, while the navigation page itself remains unchanged. , so the JavaScript variables in it will not be lost and can be used to store global data. The implementation principle is as follows:
Assume that the page on the left is link.html and the page on the right is show.html. The page structure is as follows:

You can add a statement like this next to the products displayed in show.html:
Add to Shopping Che
where link represents the navigation frame. The arrOrders array is defined in the link.html page to store the ID of the product. The function addToOrders() is used to respond to the click event of the [Purchase] link next to the product. It The received parameter id represents the id of the product. In the example, it is a product with id 32068:

In this way, you can use arrOrders to get all the products ready to be purchased on the checkout page or shopping cart browsing page.
The framework can divide a page into multiple modules with independent functions. Each module is independent of each other, but can be connected through the reference of the window object. It is an important mechanism in Web development.