XML Question

[gk]

XML
======

<bookstore>
−
<book category="COOKING">
<title lang="en">Everyday Italian</title>
<author>Giada De Laurentiis</author>
<year>2005</year>
<price>30.00</price>
</book>
−
<book category="CHILDREN">
<title lang="en">Harry Potter</title>
<author>J K. Rowling</author>
<year>2005</year>
<price>29.99</price>
</book>
−
<book category="WEB">
<title lang="en">XQuery Kick Start</title>
<author>James McGovern</author>
<author>Per Bothner</author>
<author>Kurt Cagle</author>
<author>James Linn</author>
<author>Vaidyanathan Nagarajan</author>
<year>2003</year>
<price>49.99</price>
</book>
−
<book category="WEB">
<title lang="en">Learning XML</title>
<author>Erik T. Ray</author>
<year>2003</year>
<price>39.95</price>
</book>
</bookstore>


DOM Example:
===========
The following code fragment gets the text from the first <title>
element:

getElementsByTagName("title")[0].childNodes[0].nodeValue


Question : why we have to use childNodes[0] ......see there is no child
node for the node "title"
still, why do we require this ? can we remove it ? if so, what could be
the alternative syntax ?

 

[Andy Dingley]

<title lang="en">Everyday Italian</title>


getElementsByTagName("title")[0].childNodes[0].nodeValue


Question : why we have to use childNodes[0] ......see there is no child
node for the node "title"

<title> has no child elements, but it has child node(s) that are
textNodes
You need to remember this difference! Not all nodes are elements.

 

[Joseph Kesselman]

.... and in the basic DOM API, an Element has no node value; you have to
query its descendants.

Note that XPath handles this differently; in XPath's view of the world,
the value of an element is all text contained within it. (Not just its
immediate text children, please note!)

DOM Level 3 adds an operation to retrieve the XPath-equivalent node
value... but if that new (and optional) feature isn't available in your
DOM, you have to walk the subtree and gather the contained text yourself.

 

[gk]

<title lang="en">Everyday Italian</title>


getElementsByTagName("title")[0].childNodes[0].nodeValue


Question : why we have to use childNodes[0] ......see there is no child
node for the node "title"

<title> has no child elements, but it has child node(s) that are
textNodes
You need to remember this difference! Not all nodes are elements.

i got confused now.

i believe when there is a tag < > , its called Element , so in that
sense , <title>is a Element.

and i knew Element and Node are same .

but from you comment , it means Element and Node are different thing
and in this example , the text value can be a Node !

For example, the text which comes under <title> , you are saying ..its
a TextNode.

could you please Tell, what is a Node ?
whats the difference between a Node and Element ?
please provide an example for this .

thank you

 

[Andy Dingley]

and i knew Element and Node are same .

They aren't.

Everything in the DOM is a Node. Some Nodes are Elements, some Nodes
are textNodes, some Nodes are Attributes.

 

[Joe Kesselman]

and i knew Element and Node are same

Sounds like you really need to sit down and read a good intro-to-the-DOM
tutorial, since whatever documentation you've been working from is more
than slightly confused.

(Standard pointer to the collection of articles and tutorials at
DeveloperWorks, http://www.ibm.com/xml)

 

[gk]

They aren't.

Everything in the DOM is a Node. Some Nodes are Elements, some Nodes
are textNodes, some Nodes are Attributes.

ok.

here i have found these texts in w3school

http://www.w3schools.com/dom/dom_element.asp

A common error in DOM processing is to navigate to an element node and
expect it to contain the text. However, even the simplest element node
has a text node under it. For example, in <year>2005</year>, there is
an element node (year), and a text node under it, which contains the
text (2005).

so, year is a Elemet here ? is it rule that if a node has angular
bracket then that node is called Element ?

so, what do you call you 2005 ? is it a text-node and childnode both
?

see in the code i posted in my first post , they are talking about
childnode[0] .......so, textnode ,childnode all are same ?

 

[Joe Kesselman]

so, what do you call you 2005 ? is it a text-node and childnode both

It is a text node which happens to be a child of the element that
contains it.

childnode[0] .......so, textnode ,childnode all are same ?

NO. You're confusing node types and node relationships.

The DOM is made up of nodes. Those nodes have types such as element,
text, comment, attribute, and so on. Most of the nodes are organized in
a simple tree data structure via their parent/child relationships; they
also have previous-sibling and next-sibling relationships with other
nodes. Attributes are a special case; they aren't in the main tree and
aren't either parents or children, nor do they have previous/next (since
they're unordered), but they can be retrieved from the element they
belong to.

(When you get around to using XPath and XSLT you'll find that they
describe things slightly differently, but the basic ideas are the same.)

Hope that helps.