Created
June 24, 2011 12:50
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Event delegation blog post gists
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| interface EventTarget { | |
| void addEventListener(in DOMString type, | |
| in EventListener listener, | |
| in boolean useCapture); | |
| }; | |
| var link = document.getElementById('#myLink'); | |
| // use bubbling: | |
| link.addEventListener('click', callbackFnForClick, false); | |
| // use capturing | |
| link.addEventListener('click', callbackFnForClick, true); |
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| var container = document.getElementById('myCont'); | |
| container.addEventListener('click', clickCallbackFn, false); | |
| // or | |
| delegate('click', container, 'a', clickCallbackFn); | |
| // where delegate can look like this | |
| function delegate(eventType, elementToBind, delegateTo, callbackFn) { | |
| // modern browser | |
| if (elementToBind.addEventListener){ | |
| elementToBind.addEventListener(eventType, function(evt){ | |
| // again this is very primitive and lets you | |
| // to operate only on tag selectors | |
| if(evt.target.nodeName.toLowerCase() === delegateTo.toLowerCase()) { | |
| // call callbackFn in context of evt.target with proper arguments | |
| callbackFn.call(evt.target, evt); | |
| } | |
| }, false); | |
| // IE | |
| } else if(elementToBind.attachEvent) { | |
| elementToBind.attachEvent('on' + eventType, function(evt){ | |
| if(evt.srcElement.nodeName.toLowerCase() === delegateTo.toLowerCase()) { | |
| callbackFn.call(evt.srcElement, evt); | |
| } | |
| }); | |
| } | |
| } |
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| function callbackFn(event) { | |
| alert(this) // we expect it to be clicked link element | |
| event.target // <a> in both cases | |
| event.currentTarget // this is where difference sits | |
| } | |
| // add listener for callbackFn to all link elements | |
| Y.on('click', callbackFn, 'a') | |
| // add listener to #myCont element and | |
| // delegate callbackFn to all link elements inside | |
| Y.delegate('click', callbackFn, '#myCont', 'a') |
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| function callbackFnForClick(evt) { | |
| // this is of course veeery naive and any framework method designed | |
| // for delegation will just use your callback on correct object | |
| // and in correct context in much smarter way | |
| if(evt.target.nodeName.toLowerCase() === 'a') { | |
| // do some interactions | |
| } | |
| } |
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| <a> gets clicked | |
| Bubbling: <a> → <p> → <div> → <body> | |
| Capturing: <body> → <div> → <p> → <a> |
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| var container = document.getElementById('myCont'); | |
| var links = container.getElementsByTagName('a') | |
| // gazillion of links on the page | |
| for(var i = 0, length = links.length; i < length; i++) { | |
| links[i].addEventListener('click', clickCallbackFn, false); | |
| } |
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| function callbacFnForClick(evt) { | |
| alert(evt.target) // the element that the event is fired on | |
| alert(evt.currentTarget) // the element that the event was bound to | |
| } | |
| var myCont = document.getElementById('myCont'); | |
| myCont.addEventListener('click', callbackFnForClick, false) |
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| <body> | |
| <div id="myCont"> | |
| <p><a id="myLink" href="some.html">Some link</a></p> | |
| <div> | |
| </body> |
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| <body> | |
| <div id="myCont"> | |
| <p><a id="myLink1" href="some.html">Some link 1</a></p> | |
| <p><a id="myLink2" href="some.html">Some link 2</a></p> | |
| <p><a id="myLink3" href="some.html">Some link 3</a></p> | |
| <p><a id="myLink4" href="some.html">Some link 4</a></p> | |
| <p>...</p> | |
| <p><a id="myLink57" href="some.html">Some link 57</a></p> | |
| <div> | |
| </body> |
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