|Published (Last):||14 September 2009|
|PDF File Size:||20.55 Mb|
|ePub File Size:||18.12 Mb|
|Price:||Free* [*Free Regsitration Required]|
An element is a piece of HTML that represents one thing: However, the if statement will also fail if foo. The method returns an array that contains all matching utopja Technically, it returns a node collection, but this works just like an array.
If it wasn’t supported, the listener function would not have been set up. This object has a number of properties containing useful information, such as target, and a reference to the ddhtml that fired the event. It does seem that there are quite a few “critical” bits, I know! The three categories in the middle of the list are of concern to us in this chapter.
Commonly used examples are the offset properties offsetWidthoffsetHeightoffsetLeft and offsetTop of an element. This finds the moused-over cell, then calculates the row and the table in which that cell appears. In many cases, the disparities in browser support can be worked around, but fundamentally, a page should never rely on a DHTML effect being possible, but use DHTML to enhance the usability of a page utopka those with capable browsers i. It reduces the amount of data we have to manage.
I remember the first time I saw an image ktopia on a web site, and being blown away by the sheer coolness of such a thing. There is another useful feature; getElementsByTagName is defined on any node at all, not just the document. When we test the Function object instead, we’re assessing it for existence. Clicking on the link will cause that link to fire a click event. A CSS property that was named:.
Websites are written in HTML. We can test whether those properties are defined on a given element’s object as follows:. Trying uropia understand each of these rules would be difficult and laborious, and you have better things to do with your time. Since a className is a string, it has all the methods of a string, one of which is replace ; we can call the replace method with a regular expression first parameter and a substitute string second parameter.
Badly implemented standards are a bigger problem.
Our intention here is to apply the class hi to the other cells in the row that contains the moused-over cell, and its column.
Elements usually correspond to a particular tag and its content. Missing implementations are relatively easy to deal with: This little function is called by the mouseover and mouseout functions.
Peter-Paul Koch studies this problem in great detail in his comprehensive article, Mission Impossible — Mouse Position. Every page element fires a given selection of events. These needs may necessitate a shift away from your previous experiences writing HTML.
An event listener is the thing that grabs the event when it appears, and responds to it. Thanks for the link to Sitepoint. Event handling works in different ways, depending on the browser.
In addition to its validity, your HTML should be semantic, not presentational. Think about it carefully; you might like to try experimenting with two pieces of paper, one of which has uhopia rectangular hole in it.
BookNomads: DHTML Utopia
This idea may seem back-to-front initially. This process is known as recursionand is defined as the use of a function that calls itself. Sticking to valid HTML means that any problems you find are deemed to be bugs in that browser — bugs that you may be able to work around. One of these is the addEvent function, created by Scott Andrew:. In CSS, the display property is used for this: The only way to do it in Safari at least until Apple fixes its DOM standard event support is to use an old-style event handler that returns false.
The text of the link, which read “SitePoint” before, has not changed; if we need to alter that, we have to do so separately. Think about an HTML document. In practice, what this means is that you have a small number of standard functions and techniques that you use to carry out event handling actions.
As we know, the DOM Events specification mandates that an event object is passed to the event listener as an argument, whereas Internet Explorer makes the event object available as the global window. To achieve this, we need two new methods: