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  • A few questions about how JavaScript works

    - by KayoticSully
    I originally posted on Stack Overflow and was told I might get some better answers here. I have been looking deeply into JavaScript lately to fully understand the language and have a few nagging questions that I can not seem to find answers to (Specifically dealing with Object Oriented programming. I know JavaScript is meant to be used in an OOP manner I just want to understand it for the sake of completeness). Assuming the following code: function TestObject() { this.fA = function() { // do stuff } this.fB = testB; function testB() { // do stuff } } TestObject.prototype = { fC : function { // do stuff } } What is the difference between functions fA and fB? Do they behave exactly the same in scope and potential ability? Is it just convention or is one way technically better or proper? If there is only ever going to be one instance of an object at any given time, would adding a function to the prototype such as fC even be worthwhile? Is there any benefit to doing so? Is the prototype only really useful when dealing with many instances of an object or inheritance? And what is technically the "proper" way to add methods to the prototype the way I have above or calling TestObject.prototype.functionName = function(){} every time? I am looking to keep my JavaScript code as clean and readable as possible but am also very interested in what the proper conventions for Objects are in the language. I come from a Java and PHP background and am trying to not make any assumptions about how JavaScript works since I know it is very different being prototype based. Also are there any definitive JavaScript style guides or documentation about how JavaScript operates at a low level? Thanks!

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  • Object.Watch with disabled attribute

    - by Benjamin Fleming
    <html> <head> <script type="text/javascript"> window.onload = function() { var btn = document.getElementById("button"); var tog = document.getElementById("toggle"); tog.onclick = function() { if(btn.disabled) { btn.disabled = false; } else { btn.disabled = true; } }; //btn.watch("disabled", function(prop, val, newval) { }); }; </script> </head> <body> <input type="button" value="Button" id="button" /> <input type="button" value="Toggle" id="toggle" /> </body> </html> If you test this code, the Toggle button will successfully enable and disable the other button. However, un-commenting the btn.watch() line will somehow always set the disabled tag to true. Any ideas?

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  • Class Design - Returning a List<Object> From <Object>

    - by Mike
    Given a simple class: public class Person { public string FirstName; public string LastName; public string GetFullName() { return FirstName + LastName; } } The user of this class will populate a List<Person> object by reading an Xml file or some other data source. Should the logic for populating the List be in the Person class or should it just remain in the calling class? In other words, should there be a public List<Persons> GetPersons() method in the Person class or in the calling class? Or should the data accessor be in another class altogether? I know this is a rather simplistic question but I'm just curious how others typically do it.

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  • WPF ComboBox Object Binding - not updating DataContext Object

    - by Jaysen
    Hello, I have the following scenario: 1 class called 'Widget' with the properties: ID, Code, Description 1 class called 'MyWidget' with a property: m_Widget As Widget 1 ComboBox The ComboBox has a List(Of Widget) set as the ItemSource. I create an instance of 'MyWidget' named MyWidget1 and I set the property values of the m_Widget to match one of the items in the 'ComboBox List(Of Widget)'. I then set the DataContext of the ComboBox to MyWidget1.Widget. When I change the ComboBox selected item, only the ID property of 'MyWidget1.Widget' gets updated... How do I get the object 'Widget' on 'MyWidget1' to be updated instead of just 'MyWidget1.Widget.ID'? Here is a link to a sample project demonstrating this scenario: http://www.webpersona.com/ObjectBinding.zip Thanks in advance for any help :)

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  • Is it a good object-oriented-design practice to send a pointer to private data to another class?

    - by Denis
    Hello everyone, There is well known recommendation not to include into class interface method that returns a pointer (or a reference) to private data of the class. But what do you think about public method of a class that sends to another class a pointer to the private data of the first one. For example: class A { public: void fA(void) {_b.fB(&_var)}; private: B _b; int _var; }; I think that it is some sort of data hiding damage: the private data define state of their own class, so why should one class delegate changes of its own state to another one? What do you think? Denis

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  • How to determine whether a dependency object implements a given dependency property (C# / WPF)

    - by Tim Coulter
    I am working with the classes in the System.Windows.Documents namespace, trying to write some generic code that will conditionally set the value of certain dependency properties, depending on whether these properties exist on a given class. For example, the following method assigns an arbitrary value to the Padding property of the passed FrameworkContentElement: void SetElementPadding(FrameworkContentElement element) { element.SetValue(Block.PaddingProperty, new Thickness(155d)); } However, not all concrete implementations of FrameworkContentElement have a Padding property (Paragraph does but Span does not) so I would expect the property assignment to succeed for types that implement this property and to be silently ignored for types that do not. But it seems that the above property assignment succeeds for instances of all derivatives of FrameworkContentElement, regardless of whether they implement the Padding property. I make this assumption because I have always been able to read back the assigned value. I assume there is some flaw in the way I am assigning property values. What should I do to ensure that a given dependency property assignment is ignored by classes that do not implement that property? Many thanks for your advice. Tim

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  • Object declaration in Objective-C

    - by Sahat
    Is there any difference in declaring objects in Objective-C between (1) and (2), besides the style and personal preference? (1) One-line declaration, allocation, initialization. Student *myStudent = [[Student alloc] init]; (2) Multi-line declaration, allocation, initialization. Student *myStudent; myStudent = [Student alloc]; myStudent = [myStudent init];

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  • Does this schema sound better suited for a document-oriented data store or relational?

    - by Blaine LaFreniere
    Disclaimer: let me know if this question is better suited for serverfault.com I want to store information on music, specifically: genres artists albums songs This information will be used in a web application, and I want people to be able to see all of the songs associated to an album, and albums associated to an artist, and artists associated to a genre. I'm currently using MySQL, but before I make a decision to switch I want to know: How easy is scaling horizontally? Is it easier to manage than an SQL based solution? Would the above data I want to store be too hard to do schema-free? When I think association, I immediately think RDBMSs; can data be stored in something like CouchDB but still have some kind of association as stated above?

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  • find(:all) and then add data from another table to the object

    - by Koning Baard XIV
    I have two tables: create_table "friendships", :force => true do |t| t.integer "user1_id" t.integer "user2_id" t.boolean "hasaccepted" t.datetime "created_at" t.datetime "updated_at" end and create_table "users", :force => true do |t| t.string "email" t.string "password" t.string "phone" t.boolean "gender" t.datetime "created_at" t.datetime "updated_at" t.string "firstname" t.string "lastname" t.date "birthday" end I need to show the user a list of Friendrequests, so I use this method in my controller: def getfriendrequests respond_to do |format| case params[:id] when "to_me" @friendrequests = Friendship.find(:all, :conditions => { :user2_id => session[:user], :hasaccepted => false }) when "from_me" @friendrequests = Friendship.find(:all, :conditions => { :user1_id => session[:user], :hasaccepted => false }) end format.xml { render :xml => @friendrequests } format.json { render :json => @friendrequests } end end I do nearly everything using AJAX, so to fetch the First and Last name of the user with UID user2_id (the to_me param comes later, don't worry right now), I need a for loop which make multiple AJAX calls. This sucks and costs much bandwidth. So I'd rather like that getfriendrequests also returns the First and Last name of the corresponding users, so, e.g. the JSON response would not be: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3 } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4 } } ] but rather: [ { "friendship": { "created_at": "2010-02-19T13:51:31Z", "user1_id": 2, "updated_at": "2010-02-19T13:51:31Z", "hasaccepted": false, "id": 11, "user2_id": 3, "firstname": "Jon", "lastname": "Skeet" } }, { "friendship": { "created_at": "2010-02-19T16:31:23Z", "user1_id": 2, "updated_at": "2010-02-19T16:31:23Z", "hasaccepted": false, "id": 12, "user2_id": 4, "firstname": "Mark", "lastname": "Gravell" } } ] I thought of a for loop in the getfriendrequests method, but I don't know how to implement this, and maybe there is an easier way. It must also work for XML. Can anyone help me? Thanks

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  • wpf c# databinding on object

    - by Enriquev
    Hello, say I have this control: public partial class bloc999 : UserControl { bloc999Data mainBlock = new bloc999Data(); public bloc999() { InitializeComponent(); mainBlock.txtContents = "100"; base.DataContext = mainBlock; } } in the xaml: <TextBox Margin="74,116,106,0" Name="txtContents" Text="{Binding Path=txtContents, UpdateSourceTrigger=PropertyChanged,Mode = TwoWay}" /> <TextBox Margin="74,145,106,132" Name="txtContents2" Text="{Binding Path=txtContents2, UpdateSourceTrigger=PropertyChanged,Mode = TwoWay}" /> Then I have this class: public class bloc999Data : INotifyPropertyChanged { string _txtContents; string _txtContents2; public event PropertyChangedEventHandler PropertyChanged; void NotifyPropertyChanged(string propName) { if (this.PropertyChanged != null) this.PropertyChanged( this, new PropertyChangedEventArgs(propName)); } public string txtContents2 { get { return this._txtContents2; } set { if (int.Parse(value) > int.Parse(this._txtContents)) { this._txtContents2 = "000"; } else this._txtContents2 = value; NotifyPropertyChanged("txtContents2"); } } public string txtContents { get { return this._txtContents; } set { this._txtContents = value; NotifyPropertyChanged("txtContents"); } } } Ok now say I have A button on the form and I do this in the code: mainBlock.txtContents2 = "7777777"; It puts 000 in the textbox, but If i just type in manually, in the textbox (txtContents2, the setter code is called but for some reason the textboxes value does not change, the instance value does change. help?

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  • copying the request header from request object to urlConnection object

    - by Bunny Rabbit
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // TODO Auto-generated method stub URL url = new URL("http://localhost:8080/testy/Out"); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); connection.setDoOutput(true); connection.setRequestMethod("POST"); PrintWriter out=response.getWriter(); for(Enumeration e=request.getHeaderNames();e.hasMoreElements();){ Object o=e.nextElement(); String value=request.getHeader(o.toString()); out.println(o+"--is--"+value+"<br>"); connection.setRequestProperty((String) o, value); } connection.connect(); } i wrote the above code in a servlet to post form so some alternate locations than this servlet,but its not working.is it okay to use connection.setRequestProperty to set the header fields to what they are in the incoming request to servlet.

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  • Using OpenGL drawing operations in an object-oriented setting?

    - by Lion Kabob
    I've been plowing through basic shaders and whatnot for an application I'm writing, and I've been having trouble figuring out a high-level organization for the drawing calls. I'm thinking of having a singleton class which implements a number of basic drawing operations, taking data from "user" classes and passing that to the appropriate opengl calls. I'm wondering how people do this when writing their own applications, as the internet is chock full of basic "Your first shader" tutorials, but very little on suggested organization of drawing code. My particular environment is targeted at iPad/OpenGL ES 2.0, but I think the question stands for most environments.

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  • Returning new object, overwrite the existing one in Java

    - by lupin
    Note: This is an assignment. Hi, Ok I have this method that will create a supposedly union of 2 sets. i mport java.io.*; class Set { public int numberOfElements; public String[] setElements; public int maxNumberOfElements; // constructor for our Set class public Set(int numberOfE, int setE, int maxNumberOfE) { this.numberOfElements = numberOfE; this.setElements = new String[setE]; this.maxNumberOfElements = maxNumberOfE; } // Helper method to shorten/remove element of array since we're using basic array instead of ArrayList or HashSet from collection interface :( static String[] removeAt(int k, String[] arr) { final int L = arr.length; String[] ret = new String[L - 1]; System.arraycopy(arr, 0, ret, 0, k); System.arraycopy(arr, k + 1, ret, k, L - k - 1); return ret; } int findElement(String element) { int retval = 0; for ( int i = 0; i < setElements.length; i++) { if ( setElements[i] != null && setElements[i].equals(element) ) { return retval = i; } retval = -1; } return retval; } void add(String newValue) { int elem = findElement(newValue); if( numberOfElements < maxNumberOfElements && elem == -1 ) { setElements[numberOfElements] = newValue; numberOfElements++; } } int getLength() { if ( setElements != null ) { return setElements.length; } else { return 0; } } String[] emptySet() { setElements = new String[0]; return setElements; } Boolean isFull() { Boolean True = new Boolean(true); Boolean False = new Boolean(false); if ( setElements.length == maxNumberOfElements ){ return True; } else { return False; } } Boolean isEmpty() { Boolean True = new Boolean(true); Boolean False = new Boolean(false); if ( setElements.length == 0 ) { return True; } else { return False; } } void remove(String newValue) { for ( int i = 0; i < setElements.length; i++) { if ( setElements[i] != null && setElements[i].equals(newValue) ) { setElements = removeAt(i,setElements); } } } int isAMember(String element) { int retval = -1; for ( int i = 0; i < setElements.length; i++ ) { if (setElements[i] != null && setElements[i].equals(element)) { return retval = i; } } return retval; } void printSet() { for ( int i = 0; i < setElements.length; i++) { if (setElements[i] != null) { System.out.println("Member elements on index: "+ i +" " + setElements[i]); } } } String[] getMember() { String[] tempArray = new String[setElements.length]; for ( int i = 0; i < setElements.length; i++) { if(setElements[i] != null) { tempArray[i] = setElements[i]; } } return tempArray; } Set union(Set x, Set y) { String[] newXtemparray = new String[x.getLength()]; String[] newYtemparray = new String[y.getLength()]; int len = newYtemparray.length + newXtemparray.length; Set temp = new Set(0,len,len); newXtemparray = x.getMember(); newYtemparray = x.getMember(); for(int i = 0; i < newYtemparray.length; i++) { temp.add(newYtemparray[i]); } for(int j = 0; j < newXtemparray.length; j++) { temp.add(newXtemparray[j]); } return temp; } Set difference(Set x, Set y) { String[] newXtemparray = new String[x.getLength()]; String[] newYtemparray = new String[y.getLength()]; int len = newYtemparray.length + newXtemparray.length; Set temp = new Set(0,len,len); newXtemparray = x.getMember(); newYtemparray = x.getMember(); for(int i = 0; i < newXtemparray.length; i++) { temp.add(newYtemparray[i]); } for(int j = 0; j < newYtemparray.length; j++) { int retval = temp.findElement(newYtemparray[j]); if( retval != -1 ) { temp.remove(newYtemparray[j]); } } return temp; } } // This is the SetDemo class that will make use of our Set class class SetDemo { public static void main(String[] args) { //get input from keyboard BufferedReader keyboard; InputStreamReader reader; String temp = ""; reader = new InputStreamReader(System.in); keyboard = new BufferedReader(reader); try { System.out.println("Enter string element to be added" ); temp = keyboard.readLine( ); System.out.println("You entered " + temp ); } catch (IOException IOerr) { System.out.println("There was an error during input"); } /* ************************************************************************** * Test cases for our new created Set class. * ************************************************************************** */ Set setA = new Set(0,10,10); setA.add(temp); setA.add("b"); setA.add("b"); setA.add("hello"); setA.add("world"); setA.add("six"); setA.add("seven"); setA.add("b"); int size = setA.getLength(); System.out.println("Set size is: " + size ); Boolean isempty = setA.isEmpty(); System.out.println("Set is empty? " + isempty ); int ismember = setA.isAMember("sixb"); System.out.println("Element sixb is member of setA? " + ismember ); Boolean output = setA.isFull(); System.out.println("Set is full? " + output ); //setA.printSet(); int index = setA.findElement("world"); System.out.println("Element b located on index: " + index ); setA.remove("b"); //setA.emptySet(); int resize = setA.getLength(); System.out.println("Set size is: " + resize ); //setA.printSet(); Set setB = new Set(0,10,10); setB.add("b"); setB.add("z"); setB.add("x"); setB.add("y"); Set setC = setA.union(setB,setA); System.out.println("Elements of setA"); setA.printSet(); System.out.println("Union of setA and setB"); setC.printSet(); } } The union method works a sense that somehow I can call another method on it but it doesn't do the job, i supposedly would create and union of all elements of setA and setB but it only return element of setB. Sample output follows: java SetDemo Enter string element to be added hello You entered hello Set size is: 10 Set is empty? false Element sixb is member of setA? -1 Set is full? true Element b located on index: 2 Set size is: 9 Elements of setA Member elements on index: 0 hello Member elements on index: 1 world Member elements on index: 2 six Member elements on index: 3 seven Union of setA and setB Member elements on index: 0 b Member elements on index: 1 z Member elements on index: 2 x Member elements on index: 3 y thanks, lupin

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  • Methods and properties in scheme - is object oriented programming possible in scheme?

    - by incrediman
    I will use a simple example to illustrate my question. In Java, C, or any other OOP language, I could create a pie class in a way similar to this: class Apple{ public String flavor; public int pieces; private int tastiness; public goodness(){ return tastiness*pieces; } } What's the best way to do that with Scheme? I suppose I could do with something like this: (define make-pie (lambda (flavor pieces tastiness) (list flavor pieces tastiness))) (define pie-goodness (lambda (pie) (* (list-ref pie 1) (list-ref pie 2)))) (pie-goodness (make-pie 'cherry 2 5)) ;output: 10 ...where cherry is the flavor, 2 is the pieces, and 5 is the tastiness. However then there's no type-safety or visibility, and everything's just shoved in an unlabeled list. How can I improve that? Sidenote: The make-pie procedure expects 3 arguments. If I want to make some of them optional (like I'd be able to in curly-brace languages like Java or C), is it good practice to just take the arguments in as a list (that is treat the arguments as a list - not require one argument which is a list) and deal with them that way?

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  • getting an error on jslint while creating a new object using javascript

    - by user3712689
    For some reason this code is giving a lint. I can't really figure out why. It says: 'was expecting a assignment or function call, and instead saw an expression.' What does that mean? window.onload = function (){ function SuspectOne (naam, leeftijd, wie){ this.naam = Spencer Hawes; this.leeftijd = 22; this.wie = zoon van de man; } function SuspectTwo (naam, leeftijd, wie){ this.naam = Tyrone Biggums; this.leeftijd = 28; this.wie = lokale herionejunk; } function SuspectThree (naam, leeftijd, wie){ this.naam = Ellie Campbell Hawes; this.leeftijd = 40; this.wie = vrouw van de man; } var verdachten = new Array[]; verdachten[0] = new Verdachte("Spencer Hawes", 22, "zoon van de man"); verdachten[1] = new Verdachte("Tyrone Biggums", 28, "lokale herionejunk"); verdachten[2] = new Verdachte("Ellie Spencer Hawes", 40, "vrouw van de man"); for(x=0; x<verdachten.length; x++){ console.log("De verdachte is de " + verdachten[x].leeftijd + "jaar oud " + verdachten[x].naam + ", de " + verdachten[x].wie); } }; Can someone help me with this? I would really like a lint free code.

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  • javascript. is it posible for one member of an object to access another member of that object withou

    - by joox
    For example: var myObj={ myValue="hola", asMember=function(){ alert( this.myValue ); } }; myObj.asMember(); // will work fine var asGlobal=myObj.asMember; // global alias for that member function asGlobal(); // won't work in javascript (will work in AS3, but i need js now) So the question is, can I rewrite asMember so that it could be called by global alias and without mentioning myObj at all? It's understood that if I define it: asMember=function(){ alert( myObj.myValue ); } it will work, but in my case, mentioning myObj is not acceptable even inside the function itself (because myObj may be reassigned later, but asGlobal won't change and should keep working)

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  • Accessing variables of an object of a particular class through a different class within the construc

    - by Haxed
    class Student { private String name; public Student(String name){ this.name = name; } public String getName(){ return name; } } class StudentServer { public StudentServer(){ Student[] s = new Student[30]; s[0] = new Student("Nick"); System.out.println(s[0]); // LINE 01:But this compiles, although prints junk System.out.println(s[0].getName()); // LINE 02:I get a error called cannot find symbol } public static void main(){ new StudentServer(); } } Hey, there are two lines, I want the reader to focus on, the first line prints junk as usual, but suprizingly the second one gives me an error. Do you know why ? Many Thanks

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  • Another Call to a member function get_segment() on a non-object question

    - by hogofwar
    I get the above error when calling this code: <? class Test1 extends Core { function home(){ ?> This is the INDEX of test1 <? } function test2(){ echo $this->uri->get_segment(1); //this is where the error comes from ?> This is the test2 of test1 testing URI <? } } ?> I get the error where commentated. This class extends this class: <?php class Core { public function start() { require("funk/funks/libraries/uri.php"); $this->uri = new uri(); require("funk/core/loader.php"); $this->load = new loader(); if($this->uri->get_segment(1) != "" and file_exists("funk/pages/".$this->uri->get_segment(1).".php")){ include("funk/pages/". $this->uri->get_segment(1).".php"); $var = $this->uri->get_segment(2); if ($var != ""){ $home= $this->uri->get_segment(1); $Index= new $home(); $Index->$var(); }else{ $home= $this->uri->get_segment(1); $Index = new $home(); $Index->home(); } }elseif($this->uri->get_segment(1) and ! file_exists("funk/pages/".$this->uri->get_segment(1).".php")){ echo "404 Error"; }else{ include("funk/pages/index.php"); $Index = new Index(); $Index->home(); //$this->Index->index(); echo "<!--This page was created with FunkyPHP!-->"; } } } ?> And here is the contents of uri.php: <?php class uri { private $server_path_info = ''; private $segment = array(); private $segments = 0; public function __construct() { $segment_temp = array(); $this->server_path_info = preg_replace("/\?/", "", $_SERVER["PATH_INFO"]); $segment_temp = explode("/", $this->server_path_info); foreach ($segment_temp as $key => $seg) { if (!preg_match("/([a-zA-Z0-9\.\_\-]+)/", $seg) || empty($seg)) unset($segment_temp[$key]); } foreach ($segment_temp as $k => $value) { $this->segment[] = $value; } unset($segment_temp); $this->segments = count($this->segment); } public function segment_exists($id = 0) { $id = (int)$id; if (isset($this->segment[$id])) return true; else return false; } public function get_segment($id = 0) { $id--; $id = (int)$id; if ($this->segment_exists($id) === true) return $this->segment[$id]; else return false; } } ?> i have asked a similar question to this before but the answer does not apply here. I have rewritten my code 3 times to KILL and Delimb this godforsaken error! but nooooooo....

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  • Load random swf object with jquery

    - by Eggnog
    I'm working on a site that utilizes full screen background video. I have three flash videos I'd like to load into the page which would be displayed randomly on page refresh. I know you can achieve this through action script loading the movies into one main .swf, but I'm rubbish with Flash and am looking for an alternative solution. My search so far has uncovered a method using jquery. Unfortunately my attempts to implement it have failed. I'm hoping someone more knowledgeable than myself can tell me if this technique is valid or what I'm doing wrong. Here's my code to date: <script type="text/javascript" src="files/js/swfobject.js"></script> <script type="text/javascript"> $(document).ready(function() { var sPath; var i = Math.floor(Math.random()*2); switch(i) { case 0: sPath = "flash/homepage_video.swf"; break; case 1: sPath = "flash/homepage_video.swf"; break; } // load the flash version of the image var so = new SWFObject(sPath, "flash-background", "100%", "100%"); so.addParam("scale", "exactFit"); so.addParam("movie", sPath); // NOTE: the sPath variable is also used here so.addParam("quality", "high"); so.addParam("wmode", "transparent"); so.write("homeBackground"); // NOTE: The value in this call to write() MUST match the name of the // HTML element (<div>) you're expecting the swf to show up in }); </script> <body> <div id="homeBackground"> <p>This is alternative content</p> </div> </body> I'm open to other suggestions that don't involve jquery (php perhaps). Thanks.

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