PrototypeJavascriptExtensions

PrototypeDocumentation » PrototypeJavascriptExtensions

Extensions to various classes

This collection of classes and functions extends existing Javascript classes and functions. They simplfy such things as manipulating text, adding keyboard commands, adding inheretance, and other random things.

Extensions to the JavaScript classes

One of the ways the prototype.js library adds functionality is by extending the existing JavaScript classes.

Extensions for the Object class

Method	Kind	Arguments	Description
extend(destination, source)	static	destination: any object, source: any object	Provides a way to implement inheritance by copying all properties and methods from source to destination.
extend(object)	instance	any object	Provides a way to implement inheritance by copying all properties and methods from the given object.

Extensions for the Number class

Method	Kind	Arguments	Description
toColorPart()	instance	(none)	Returns the hexadecimal representation of the number. Useful when converting the RGB components of a color into its HTML representation.

Extensions for the Function class

Method	Kind	Arguments	Description
bind(object)	instance	object: the object that owns the method	Returns an instance of the function pre-bound to the function(=method) owner object. The returned function will have the same arguments as the original one.
bindAsEventListener(object)	instance	object: the object that owns the method	Returns an instance of the function pre-bound to the function(=method) owner object.The returned function will have the current event object as its argument.

Let's see one of these extensions in action.


<input type=checkbox id=myChk value=1 /> Test?
<script>
    //declaring the class
    var CheckboxWatcher = Class.create();

    //defining the rest of the class implmentation
    CheckboxWatcher.prototype = {
        initialize: function(chkBox, message) {
            this.chkBox = $(chkBox);
            this.message = message;
            //assigning our method to the event
            this.chkBox.onclick = this.showMessage.bindAsEventListener(this);
        },

        showMessage: function(evt) {
            alert(this.message + ' (' + evt.type + ')');
        }
    };

    var watcher = new CheckboxWatcher('myChk', 'Changed');
</script>

Extensions for the String class

Method	Kind	Arguments	Description
stripTags()	instance	(none)	Returns the string with any HTML or XML tags removed
escapeHTML()	instance	(none)	Returns the string with any HTML markup characters properly escaped
unescapeHTML()	instance	(none)	The reverse of escapeHTML()

Extensions for the document DOM object

Method	Kind	Arguments	Description
getElementsByClassName(className)	instance	className: name of a CSS class associated with the elements	Returns all the elements that are associated with the given class name.

Extensions for the Event object

Property	Type	Description
KEY_BACKSPACE	Number	8: Constant. Code for the Backspace key.
KEY_TAB	Number	9: Constant. Code for the Tab key.
KEY_RETURN	Number	13: Constant. Code for the Return key.
KEY_ESC	Number	27: Constant. Code for the Esc key.
KEY_LEFT	Number	37: Constant. Code for the Left arrow key.
KEY_UP	Number	38: Constant. Code for the Up arrow key.
KEY_RIGHT	Number	39: Constant. Code for the Right arrow key.
KEY_DOWN	Number	40: Constant. Code for the Down arrow key.
KEY_DELETE	Number	46: Constant. Code for the Delete key.
observers:	Array	List of cached observers. Part of the internal implementation details of the object.

Method	Kind	Arguments	Description
element(event)	static	event: an Event object	Returns element that originated the event.
isLeftClick(event)	static	event: an Event object	Returns true if the left mouse button was clicked.
pointerX(event)	static	event: an Event object	Returns the x coordinate of the mouse pointer on the page.
pointerY(event)	static	event: an Event object	Returns the y coordinate of the mouse pointer on the page.
stop(event)	static	event: an Event object	Use this function to abort the default behavior of an event and to suspend its propagation.
findElement(event, tagName)	static	event: an Event object, tagName: name of the desired tag.	Traverses the DOM tree upwards, searching for the first element with the given tag name, starting from the element that originated the event.
observe(element, name, observer, useCapture)	static	element: object or id, name: event name (like 'click', 'load', etc), observer: function to handle the event, useCapture: if true, handles the event in the capture phase and if false in the bubbling phase.	Adds an event handler function to an event.
stopObserving(element, name, observer, useCapture)	static	element: object or id, name: event name (like 'click'), observer: function that is handling the event, useCapture: if true handles the event in the capture phase and if false in the bubbling phase.	Removes an event handler from the event.
_observeAndCache(element, name, observer, useCapture)	static		Private method, do not worry about it.
unloadCache()	static	(none)	Private method, do not worry about it. Clears all cached observers from memory.

Let's see how to use this object to add an event handler to the load event of the window object.


<script>
    Event.observe(window, 'load', showMessage, false);

    function showMessage() {
      alert('Page loaded.');
    }
</script>

New objects and classes defined by prototype.js

Another way the library helps you is by providing many objects implement both support for object oriented designs and common functionality in general.

The PeriodicalExecuter object

This object provides the logic for calling a given function repeatedly, at a given interval.

Method	Kind	Arguments	Description
ctor(callback, interval)	constructor	callback: a parameterless function, interval: number of seconds	Creates one instance of this object that will call the function repeatedly.

Property	Type	Description
callback	Function()	The function to be called. No parameters will be passed to it.
frequency	Number	This is actually the interval in seconds
currentlyExecuting	Boolean	Indicates if the function call is in progress

The Prototype object

The Prototype object does not have any important role, other than declaring the version of the library being used.

Property	Type	Description
Version	String	The version of the library
emptyFunction	Function()	An empty function object

The Class object

The Class object is used when declaring the other classes in the library. Using this object when declaring a class causes the to new class to support an initialize() method, which serves as the constructor.

See the sample below.


<script>
    //declaring the class
    var MySampleClass = Class.create();

    //defining the rest of the class implmentation
    MySampleClass.prototype = {
        initialize: function(message) {
            this.message = message;
        },

        showMessage: function(ajaxResponse) {
            alert(this.message);
        }
    };

    //now, let's instantiate and use one object
    var myTalker = new MySampleClass('hi there.');
    myTalker.showMessage(); //displays alert
</script>

Method	Kind	Arguments	Description
create(*)	instance	(any)	Defines a constructor for a new class