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Enhacing the content with JavaScript

2015-09-14 15:18 453 查看
What not to do :
In theory , you could use JavaScript to add important content to a web page.
However, that would be a very bad idea, because there would be no room for graceful degradation.
Visitors lacking the necessary JavaScript support would never see the content.

The markup : HTML, XHTML, or HTML5
For the markup, its up to you whether to use HTML or XHML.
The important thing is that whichever document type you choose, the markup validates to the
specified DOCTYPE declaration.

With XHTML, all the tags must be closed. That includes stand-alone elements like <img> and <br>
which must be written with a closing slash: <img /> and <br />
To use the XHTML DOCTYPE, you include this at the begining of your document :

<!DOCTYPE html  PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strick.dtd" >


Another option that you may like even better is to use the HTML5 DOCTYPE. The HTML5 DOCTYPE is
very simple (just 15 characters) :

<!DOCTYPE html>


You can create useful scripts like these using just a handful of DOM methods and porperties.
Having well-structured markup is an important prerequisite when you are enhancing content
with DOM scripts.
As a recap, these are the most useful methods for retrieving information from a document :

getElementById

getElementsByTagName

getElementsByName

getAttribute

These are the most useful methods for attaching information to a document :

createElement

createTextNode

appendChild

insertBefore

setAttribute

By combining those methods, you can create very powerful DOM scripts.
Always remember to use JavaScript to enhance the content of your documents, rahter than
creating any core content directly with the DOM.
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