Crazy XML study notes (5) -----------XML DOM
DOM (Document Object Model, Document Object Model) defines a set of standard methods for accessing and manipulating documents.
XML DOM
##XML DOM (XML Document Object Model) Definition A set of standard methods for accessing and manipulating XML documents.
DOM View XML documents as a tree structure. All elements can be accessed through the DOM tree. Their contents can be modified or deleted, and new elements created. Elements, their text, and their attributes are all considered nodes.
In the following example, we use a DOM reference to get the text from the <to> element:
xmlDoc.getElementsByTagName("to")[0].childNodes[0].nodeValue
xmlDoc - XML document created by the parser
getElementsByTagName("to")[0] - First<to> element
childNodes[0] - The first child element of the <to> element (text node)
nodeValue - the value of the node (the text itself)
HTML DOM
##HTML DOM (HTML Document Object Model) Definition A set of standard methods for accessing and manipulating HTML documents.All HTML elements can be accessed through the HTML DOM.
In the following example, we use a DOM reference to change the text of the HTML element with id="to":
document.getElementById("to").innerHTML=
document - HTML document
- ##getElementById("to")
- where id=" to" HTML element
- innerHTML
- The inner text of the HTML element
Parse XML file - cross-browser example
The following code Load an XML document ("note.xml") into the XML parser:
<html>
<head>
<script type="text/javascript">
function parseXML()
{
try //Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
}
catch(e)
{
try //Firefox, Mozilla, Opera, etc.
{
xmlDoc=document.implementation.createDocument("","",null);
}
catch(e)
{
alert(e.message);
return;
}
}
xmlDoc.async=false;
xmlDoc.load("note.xml");
document.getElementById("to").innerHTML=
xmlDoc.getElementsByTagName("to")[0].childNodes[0].nodeValue;
document.getElementById("from").innerHTML=
xmlDoc.getElementsByTagName("from")[0].childNodes[0].nodeValue;
document.getElementById("message").innerHTML=
xmlDoc.getElementsByTagName("body")[0].childNodes[0].nodeValue;
}
</script>
</head>
<body onload="parseXML()">
<h1>W3School.com.cn Internal Note</h1>
<p><b>To:</b> <span id="to"></span><br />
<b>From:</b> <span id="from"></span><br />
<b>Message:</b> <span id="message"></span>
</p>
</body>
</html>Output: To:
GeorgeFrom: JohnMessage: Don't forget the meeting!
Important Note
To extract the text "John" from XML, the syntax is:
getElementsByTagName("from")[0].childNodes[0].nodeValueIn this XML example, there is only one <from> tag, but you still need to specify the bottom of the array Tag [0] because the XML parser method getElementsByTagName() returns an array of all <from> nodes.
Parsing XML String - Cross-Browser Example
The code below loads and Parse an XML string:
<html>
<head>
<script type="text/javascript">
function parseXML()
{
text="<note>";
text=text+"<to>George</to>";
text=text+"<from>John</from>";
text=text+"<heading>Reminder</heading>";
text=text+"<body>Don't forget the meeting!</body>";
text=text+"</note>";
try //Internet Explorer
{
xmlDoc=new ActiveXObject("Microsoft.XMLDOM");
xmlDoc.async="false";
xmlDoc.loadXML(text);
}
catch(e)
{
try // Firefox, Mozilla, Opera, etc.
{
parser=new DOMParser();
xmlDoc=parser.parseFromString(text,"text/xml");
}
catch(e)
{
alert(e.message);
return;
}
}
document.getElementById("to").innerHTML=
xmlDoc.getElementsByTagName("to")[0].childNodes[0].nodeValue;
document.getElementById("from").innerHTML=
xmlDoc.getElementsByTagName("from")[0].childNodes[0].nodeValue;
document.getElementById("message").innerHTML=
xmlDoc.getElementsByTagName("body")[0].childNodes[0].nodeValue;
}
</script>
</head>
<body onload="parseXML()">
<h1>W3School.com.cn Internal Note</h1>
<p><b>To:</b> <span id="to"></span><br />
<b>From:</b> <span id="from"></span><br />
<b>Message:</b> <span id="message"></span>
</p>
</body>
</html>Output: To: GeorgeFrom: JohnMessage: Don't forget the meeting!
Note: Internet Explorer uses the loadXML() method to To parse XML strings, other browsers use DOMParser objects.
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