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A large subset of DHTML scripts work by setting on page load some event listeners that will be called as various elements in the browser fire events. Instead, it offers a proprietary and different way to hook up event listeners and gain access to event data.
The top-left corner of the big image should be in the top-left corner of the viewing area: The childNodes array may contain nothing if the node has no children such nodes are called leaf nodes. Then, if that checkbox is checked, we open the link in a new window:. This event is fired jsing the document has finished loading, to signal that all HTML elements are now available. Think wweb an HTML document.
When the user mouses over the thumbnail, that thumbnail could become a “viewing area” in which a snippet of the full-sized image is shown. Although the full definition of CSS allows you to do some fairly amazing things, and to control the presentation of your pages to a high degree, not every browser supports everything that CSS has to offer. Many designers alter style properties to make an element appear or disappear.
The techniques we have explored in this chapter are at their most powerful when we combine the dynamic capabilities of DHTML with the page styling of CSS. This is the easiest way to ensure that a browser that returns a nodeName of Aand one that returns a nodeName moern awill both be handled correctly by the function.
The upshot of this exercise is that all the cells in the same column as the moused-over utpia will have class hi ; the table row containing the cell will also have class hi.
Each CSS property is a property of that style property, with its name slightly transformed: One of the important things the figure illustrates is that the text inside an element is not part of that element.
If it wasn’t supported, the listener function would not have been set up. The next level of DOM manipulation, above and rhtml changing the properties of elements that are already there, is to add and remove elements dynamically. We assign the link variable to each link, as a way to simplify the following code.
Forms and Validation and the section explaining how to integrate client and server-side validation is a fantastic thing to include in a book like this. When we click a link, that link fires a click event, and handleLink is run.
If, before setting up the event listeners, you check that the browser supplies all the DOM features required by the code, event listeners will not be set up for browsers tuopia do not support those features. As it turns out, this event has no default action. This is called event bubbling ; an event “bubbles” up through the DOM tree, starting with the target element, until it reaches the top.