JavaScript framework (iframe) operation summary_javascript skills

Overview of Framework Programming

An HTML page can have one or more subframes, which are marked with

References between frames

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

Copy the code The code is as follows:

window. frames["frameName"];
window.frames.frameName
window.frames[index]

Among them, the word window can also be replaced or omitted with self, assuming frameName is the first one on the page Frame, the following writing methods are equivalent:

Copy code The code is as follows:

self.frames[ "frameName"]
self.frames[0]
frames[0]
frameName

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:

Copy the code The code is as follows:

window.frames["frameName"];

This refers to the subframe named frameName in 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:

Copy code The code is as follows:

window.frames["frameName"].frames["frameName2"];

In this way, the second-level sub-frame is referenced, and so on, a multi-layer framework can be implemented citation.

2． Reference from child frame to parent frame

Each window object has a parent attribute, representing its parent frame. If the frame is already a top-level frame, window.parent also represents the frame itself.

3． References between sibling frameworks

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:

Copy code The code is as follows:

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

Copy code The code is as follows:

self.parent.frames["frame2"];

4. Mutual references between frameworks at different levels

The hierarchy of frames is for top-level frames. 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:

Copy code The code is as follows:

self.parent.frames["childName"].frames["targetFrameName"];

5． Reference to the top-level frame

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:

Copy code Code As follows:

//Determine whether this frame is a top-level frame
if(self==top){
//dosomething
}

Change the loading page of the frame

The reference to the frame is a reference to the window object. Using the location attribute of the window object, you can change the navigation of the frame, for example:

Copy code The code is as follows:

window.frames[0].location="1.html";

This will redirect the page of the first frame in the page to 1 .html, taking advantage of this property, you can even use a single link to update multiple frames.

Copy code The code is as follows:

< ;!--somecode-->
link

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:

Copy code The code is as follows:

function hello(){
alert("hello,ajax!");
}
window.hello();

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:
var a=1;
alert(window.a);[/code]
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 left page is link.html and the right page is show.html. The page structure is as follows:

Copy code The code 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 an id of 32068:

Copy the code The code is as follows:

var arrOrders=new Array();
function addToOrders(id){
arrOrders.push(id);
}

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. In Ajax development, you can also use hidden frames to implement various techniques. When introducing Ajax example programming later, you will find that this technology will be used to upload files without refreshing and solve the forward and backward problems of Ajax.