Javascript dom event
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This document discusses DOM (Document Object Model) and events in JavaScript. It covers DOM node retrieval, the document tree structure, child, sibling and parent node relationships, DOM manipulation methods like appendChild and innerHTML, event handling and the bubbling and default behaviors of events.
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Javascript dom event
- 1. Click to add Text Javascript Presented by Bunlong VAN http://geekhmer.github.io DOM & Event
- 3. DOM •DOM (Document Object Modeling) •Retrieving Nodes • document.getElementById(id) • document.getElementsByName(name) • Node.getElementsByTagName(tagName)
- 4. Document Tree Structure <html> <body> <h1>Heading 1</h1> <p>Paragraph.</p> <h2>Heading 2</h2> <p>Paragraph.</p> </body> </html> #text H1 P H2 BODY #document HTML HEAD #text P #text #text
- 5. child, sibling, parent BODY H1 P H2 #text #text P #text #text lastChild lastChild lastChild lastChild lastChild firstChild firstChild firstChild firstChild firstChild
- 6. child, sibling, parent (Con.) BODY H1 P H2 #text #text P #text #text lastChild lastChild lastChild lastChild lastChild firstChild firstChild firstChild firstChild firstChild nextSibling nextSibling nextSibling previousSibling previousSibling previousSibling
- 7. child, sibling, parent (Con.) H1 #text lastChild P H2 P #text #text #text lastChild lastChild lastChild lastChild firstChild firstChild firstChild firstChild firstChild nextSibling nextSibling nextSibling previousSibling previousSibling previousSibling parentNode parentNode parentNode parentNode parentNode BODY
- 8. child, sibling, parent (Con.) BODY H1 P H2 #text #text P #text #text firstChild firstChild firstChild firstChild firstChild nextSibling nextSibling nextSibling
- 9. Child Nodes BODY 0 1 2 P childNodes H1 H2 P 3
- 10. Style •node.style.stylename •background-color •border-radius •font-size •list-style-type •word-spacing •z-index •backgroundColor •borderRadius •fontSize •listStyleType •wordSpacing •zIndex
- 11. Making Elements document.createElement(tagName); document.createTextNode(text); node.cloneNode(); // clone an individual element node.cloneNode(true); // clone an element and all of its des
- 12. Linking Ements node.appendChild(new); node.insertBefore(new, sibling); node.replaceChild(new, old); old.parentNode.replaceChild(new, old);
- 13. Removing Elements node.removeChild(old); // It returns the node old.parentNode.removeChild(old);
- 14. innerHTML •The W3C standard does not provide access to the HTML parser •All browsers implement Microsoft's innerHTML property •node.innerHTML = “<p>this is text</p>”;
- 15. Which Way is Better? •It is better to build or clone elements and append them to the document? •Or is it better to complile an HTML text and use innerHTML to realize it? •Favor clean code and easy maintenance •Favor performance only in extreme cases
- 16. Event •The browser has an event-driven, single-threaded, asynchronous programming model •Events are targeted to particular nodes •Event cause the invocation of event handler functions
- 17. Mouse Event The target is the topmost (z-index) node containing the cursor: •click •dblclick •mousedown •mousemove •mouseout •mouseover •mouseup
- 18. Input Event The target is the node having focus: •blur •change •focus •keydown •keyup •reset •submit
- 19. Event Handler •Classic – node[“on” + type] = handler; •Microsoft – node.attachEvent(“on” + type, handler); •W3C – node.addEventListener(type, handler, false); var handler = function(e) { e = e || event; var target = e.target || e.srcElement; … }
- 20. Bubbling Bubbling means that the event is given to the target, and then its parent, and so on until the event is canceled.
- 21. Why Bubble? •Suppose you have 100 draggable objects •You could attach 100 sets of event handlers to those objects •Or you could attach one set of event handlers to the container of the 100 objects
- 22. Cancel Bubbling •Cancel bubbling to keep the parent nodes from seeing th event: e.cancelBubble = true; If(e.stopPropagation) { e.stopPropagation(); }
- 23. Prevent Default Action •An event handler can prevent a browser action associated with the event (such as submitting a form): e.returnValue = false; If(e.preventDefault) { e.preventDefault(); } Return false;