JavaScript with YUI

Hacking With YUIRajat Pandit ([email protected])

1Thursday, September 24, 2009

YUI Core


Getting Started• Remember the mantra

‘GLOBAL VARIABLES ARE EVIL!!’

• Namespace before you start

YAHOO.namespace("ipc");YAHOO.ipc.foo = function(o) { alert(o);}


YAHOO.lang• Contains utilities functions

• YAHOO.lang.isArray([a,b])

• YAHOO.lang.isBoolean(val)

• YAHOO.lang.isNull(null) // true, false for undefined

• YAHOO.lang.isUndefined(v)

• YAHOO.lang.isFunction(function() {})

• YAHOO.lang.isNumber(o)

• YAHOO.lang.isObject(o)

• YAHOO.lang.isString(s)


YAHOO.lang

• YAHOO.lang.hasOwnProperty(o,p)

Very useful method to check if the property available in the object is its own or inherited via prototypal inheritance


YAHOO.lang• Extending Class is pretty straightforward

YAHOO.namespace('ipc'); // namespaceYAHOO.ipc.mc = function(info) { alert('class: ' + info);}YAHOO.ipc.mc.prototype.testMethod = function(info) { alert('class1: ' + info);}

// new classYAHOO.ipc.h2h = function(info) { YAHOO.ipc.h2h.superclass.constructor.class(this, info); alert('class2: ' + info);}

// h2h is to extend from mcYAHOO.lang.extend(YAHOO.ipc.h2h, YAHOO.ipc.mc);


YAHOO.lang• Overriding testMethod in the inherited

class and also calling the parent method

YAHOO.ipc.h2h.prototype.testMethod = function(info) { // chain the method by calling the parent YAHOO.ipc.h2h.superclass.testMethod.class(this, info); alert('class2: ' + info);};

// creating new instancevar h2hInstance = new YAHOO.ipc.h2h("constructor");h2hInstance.testMethod("testmethod");


YAHOO.lang• YAHOO.lang.augment allows you to

copy properties from one object to anotherYAHOO.ipc.test1 = function(){};YAHOO.ipc.test1.prototype ={ foo: 10, bar: function() { console.log('blah'); }}YAHOO.ipc.test2 = function() {};YAHOO.lang.augment(YAHOO.ipc.test2, YAHOO.ipc.test1);

now test2 object has the propertiesYAHOO.ipc.test2.foo returns 10;


YAHOO.log• Very useful for debugging where firebug

doesn’t work

• Writing one logging/debugging solution so that it works across all browsers

YAHOO.log(‘debug msg’, ‘log level’, ‘class name’)


YAHOO.log• Shameless Plug I

http://www.yuiblog.com/blog/2008/07/01/logger-bookmarklet/http://blog.rajatpandit.com/sandbox/yuilogger/index.html


http://blog.rajatpandit.com/sandbox/yuilogger/index.html

http://blog.rajatpandit.com/sandbox/yuilogger/index.html

YAHOO.util


YAHOO.util.Region• Useful API if you are trying to detect if objects are

overlapping or intersecting with any other elements.

• Very useful for implementing drag and drop interactions

YAHOO.util.Region.contains(region)YAHOO.util.Region.intersect(region)YAHOO.util.Region.union(region)


YAHOO.util.Point

• In case you are looking for something more specific like a pixel on the screen

• More API details available here

http://developer.yahoo.com/yui/docs/module_dom.html


YAHOO.util.Dom

• Very useful API that allows you to do stuff to the DOM

• You can pass an actual node object or its ID, both works


YAHOO.util.Dom• Get positional information for elements

• YAHOO.util.Event.getXY(e) does something similar, tells you where the event happened

// get valuesYAHOO.util.Dom.getXY()YAHOO.util.Dom.getY() YAHOO.util.Dom.getX()

// set valuesYAHOO.util.Dom.setXY()YAHOO.util.Dom.setX()YAHOO.util.Dom.setY()


YAHOO.util.Dom• Modify styles and classes of DOM nodes

YAHOO.util.Dom.setStyle(el, '<name>', '<value>');YAHOO.util.Dom.getStyle(el, '<name>');YAHOO.util.Dom.hasClass(el, '<name>');YAHOO.util.Dom.addClass(el, '<name>');YAHOO.util.Dom.removeClass(el, '<class to remove>');YAHOO.util.Dom.replaceClass(el, oldclassname, newclassname)


YAHOO.util.Dom

• Get all nodes with a specified class name starting from a particular node of a particular type

• document.getElementsByClassName(c) Works for Firefox not for IE

YAHOO.util.Dom.getElementsByClassName(classname, tagName, rootNode)


YAHOO.util.Dom• Provides the missing DOM API, without

messing up the actual objects

• Keeps it nice and clean

• More interesting API methods at:http://developer.yahoo.com/yui/docs/

YAHOO.util.Dom.insertAfter(newnode, refNode)YAHOO.util.Dom.isAncestor(haystack, needle)YAHOO.util.Dom.getNextSibling(node)YAHOO.util.Dom.getAncestorByClassName(node, classname)YAHOO.util.Dom.getAncestorByTagName(node, tagname)


YUI Event

• Two components

•YAHOO.util.Event

•YAHOO.util.CustomEvent


YAHOO.util.Event• Basic Event Handling

• Three easy steps

• Define a callback function

• Define the element (get name or actual node)

• Attach callback function to the eventYAHOO.util.Event.addListener(‘el’, ‘click’ fnCallback)YAHOO.util.Event.addListener(

[el1, el2, el3], 'click', fnCallBack

);


YAHOO.util.Event• Points to note:

• Attach an event only after the element is available in the DOM, typically after window.onload event

• YUI does the scope correction in the event handler. Provides access to event and currentTarget more consistently

• Also allows you to pass arbitrary object to the handler, the alternate to this is passing values via a) closures b) circular references both complicated ways of doing things.


YAHOO.util.Event• Callback Function Signature

function fnCallback(e, obj) { // do stuff here}

// passes myobj is the second parameter

YAHOO.util.Event.addListener(el, 'click', fnCallback, myobj);

// if we pass true as the final parameter, the custom // object that is passed is used for the execution scope // (so it becomes 'this' in the callback function)

YAHOO.util.Event.addListener(el, 'click', fnCallback, myobj, true);


YAHOO.util.Event• Event handler signature continued...

// or pass a totally different mydata = obj // and myobject = this inside the callback function

YAHOO.util.Event.addListener(el, 'click', fnCallback, mydata, myobject);


Removing Events• Remember IE6 and all its loveliness of

memory leaks??

• Ensure that you have removed all its listeners before you remove a node in DOMYAHOO.util.Event.removeListener(el, ‘click’, fnCallback)

// if reference to the callback function isn’t // available, the following will remove all // listenersYAHOO.util.Event.removeListeners(el, ‘click’)


Removing Events• To remove all event handlers

• To recurse through all children and remove all listeners

• To remove listeners only for a particular event

YAHOO.util.Event.purgeEvent(el)

YAHOO.util.Event.purgeEvent(el, true)

YAHOO.util.Event.purgeEvent(el, false, ‘click’)


Getting all listeners• You can get the list of all the attached

listenersvar listeners = YAHOO.util.Event.getListeners(el)

// the listener object has the following structurelistener = { type: ‘’, // the event type fn: ‘’, // function to execute, event handler obj: ‘’, // custom object that was passed adjust: ‘’// scope correction, this or custom obj}


When to attach handlers?

• Do stuff / attach handlers only when you are sure that the DOM is now fully availablefunction init() { console.log(‘blah’);}YAHOO.util.Event.onDOMReady(init)


Custom Events• They are awesome!!

• You might want to do multiple things when something happens

• One way is to write all the functions invocations one after the other

• Problem happens for AJAX interactions which run in the async. model

• You can create your own custom events, it uses the delegation pattern.


Custom Events• Shameless Plug II

http://blog.rajatpandit.com/2008/02/22/yui-custom-event/

• Three easy steps:

• Step 1: Define the custom event

• Step II: Make methods subscribe to the event to be fired, when that happens

• Step III: Fire the event when you think its the right time

var onMyCustomEvent = new YAHOO.util.CustomEvent(‘onmycustomevent’)

onMyCustomEvent.subscribe(method1)onMyCustomEvent.subscribe(method2)

onMyCustomEvent.fire()


Custom Events• You can also pass arguments to the

subscribed methods when firing the event

onMyCustomEvent.fire({action: ‘fire’});

function method1(event, arg, obj) {}

// event: returns the event object// arg: is the set of arguments passed in the fire event// obj: is the argument that is passed to the subscribe method


YUI Components• Loads of many hidden gems, widgets etc in the library

• Spend some time at looking at the documentation, tons of examples and API docs

YUI CORE YUI Library Utilities

YUI Controls / Widgets YUI CSS Tools


References• YUI Homepage

http://developer.yahoo.com/yui/

• YUI Theater for presentationshttp://developer.yahoo.com/yui/theater/

• API Documentationhttp://developer.yahoo.com/yui/docs/

• YUI 3 - In beta 1(as on 16th September 2009)http://developer.yahoo.com/yui/3/




http://developer.yahoo.com/yui/theater/

http://developer.yahoo.com/yui/theater/

http://developer.yahoo.com/yui/docs/

http://developer.yahoo.com/yui/docs/

http://developer.yahoo.com/yui/3/

http://developer.yahoo.com/yui/3/

DEMO


Technology

JavaScript with YUI