JavaScript and DOM
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The document discusses the Document Object Model (DOM) and how it can be used with JavaScript to dynamically manipulate HTML and XML documents. It provides an overview of the DOM levels defined by the W3C, DOM node types like elements and text, and methods for accessing and modifying the DOM tree like getElementById() and setAttribute(). It also includes examples of how to add, remove and change DOM nodes with JavaScript.
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JavaScript and DOM
- 1. Document Object Model and JavaScript Jussi Pohjolainen Tampere University of Applied Sciences
- 2. W3C DOM • DOM – Document Object Model – cross-‐ plaDorm and language-‐independent convenFon for interacFng with objects in HTML and in XML. • With DOM you can manipulate html/xml document! Dynamic html! • Public interface available: hPp://www.w3.org/ DOM/DOMTR
- 3. W3C DOM Levels • ( DOM Level 0 and Intermediate DOM ) – Not W3C Standards, used in Netscape 2 (Level 0) and Netscape 4 (Intermediate DOM) • DOM Level 1 – 1998: Ability to change enFre HTML or XML document • DOM Level 2 – 2001: Introduces “getElementById” funcFon, event model and support for XML namespaces • DOM Level 3 – 2004: XPath, keyboard event handling
- 5. DOM Programming Intro • DOM is a model that describes how all elements in an html page are related to topmost structure: document itself • Can influence the document – See: hPp://www.w3.org/TR/REC-‐DOM-‐Level-‐1/ introducFon.html • Possible to read, modify and delete tags
- 6. Node • In DOM, each object is Node • In this – <p>Hello</p> • You have two nodes – 1) element node -‐ p – 2) text node -‐ "Hello" • Text node is child node of p element. P element is parent node of the text node
- 7. Node Example <p>This is a <strong>paragraph</strong></p> <p> | -------------- | | This is a <strong> | | paragraph
- 8. APribute Node <a href=“http://www.tamk.fi”>TAMK</a> <a> ----------------- | | TAMK href | http://www.tamk.fi
- 9. Different Nodes • Element node: p, img, a • Text node: sometext • APribute node: src
- 10. DOM Level 1: To Access DOM tree • X can be some node – var parent = x.parentNode; – var firstchild = x.childNodes[0]; • How to get reference to x?
- 11. Document object
- 12. Access var title = document.firstChild.firstChild.lastChild; // document.html.head.title var title = document.firstChild.childNodes[0].childNodes[ 0];
- 13. Gelng Element Easier Way var x = document.getElementsByTagName(‘strong')[0] var x = document.getElementById('hereweare');
- 14. Changing the Node // <a href=“” id=“someId”>Link</p> var x = document.getElementById(’someId'); x.firstChild.nodeValue = “Hello!”; x.setAttribute(“href”, “http:/…”);
- 15. Inner HTML // <a href=“” id=“someId”>Link</p> var x = document.getElementById(’someId'); x.innerHTML = “Hello!”; // innerHTML is NOT W3C Standard and it’s // slower…
- 16. CreaFng and Removing Nodes var x = document.createElement(’hr'); document.getElementById('inserthrhere').appendChild(x); var node = document.getElementById('inserthrhere') node.removeChild(node.childNodes[0]); var x = document.createTextNode(’SomeText'); document.getElementById('hereweare').appendChild(x);
- 17. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> <meta http-equiv="content-type" content="application/xhtml+xml; charset=utf-8" /> <script type="text/javascript"> //<![CDATA[ function change() { // Get list of ALL <h1> - elements var listOfHeading1 = window.document.getElementsByTagName("h1"); // Find the first <h1> - element in the list var heading1 = listOfHeading1[0]; // Get the child - element of the first <h1> - element (Text) var text = heading1.firstChild; // Replace the text text.data = "Hello from JS!"; } //]]> </script> </head> <body> <h1>Title</h1> <input type="submit" onClick="change();" value="click!"/> </body> </html>
- 18. <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title></title> <meta http-equiv="content-type" content="application/xhtml+xml; charset=utf-8" /> <script type="text/javascript"> //<![CDATA[ function change() { // Reference to the table - element var table = document.getElementById("mytable"); var tr = document.createElement("tr"); // <tr> var td1 = document.createElement("td"); // <td> var td1Text = document.createTextNode("New Cell"); // "New Cell" td1.appendChild(td1Text); // <td>New Cell</td> var td2 = document.createElement("td"); // <td> var td2Text = document.createTextNode("New Cell"); // "New Cell" td2.appendChild(td2Text); // <td>New Cell</td> tr.appendChild(td1); tr.appendChild(td2); table.appendChild(tr); } //]]> </script> </head> <body> <table id="mytable" border="1"> <tr><td> </td><td> </td></tr> <tr><td> </td><td> </td></tr> <tr><td> </td><td> </td></tr> </table> <input type="submit" onClick="change();" value="Add Row"/> </body> </html>
Editor's Notes
- See:http://en.wikipedia.org/wiki/Comparison_of_layout_engines_(Document_Object_Model)Trident: IE 4.0 ->Tasman: IE For MacPresto: Opera