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JavaScript - Hashes/objects In Object Prototypes
Hi all,
The result of the code below is slightly surprising to me. If you define an object type through a prototype, and that object has a property which is a hash, the value of that hash is shared between all instances of that type. I understand the way around this (e.g. define "myHash" as its own object, and call this.myHash = new MyHash() in the object's constructor), but can someone describe to me exactly why the property "a" and the property "myHash" behave differently in the example below? Code: var MyType = function() {}
MyType.prototype = {
a: null,
myHash: {
b: null
}
}
var instance1 = new MyType();
var instance2 = new MyType();
instance1.a = "a1";
instance2.a = "a2";
instance1.myHash.b = "b1";
instance2.myHash.b = "b2";
alert(instance1.a); // = "a1"
alert(instance1.myHash.b); // = "b2"
Thanks! Similar TutorialsIn the spirit of the season, I wanted to make it snow on my website. So I began digging. Eventually I ended up with a script that moved an image element down the page in a snowflake-like manner. The problem with it was it was dependant on an img element for every flake - simply no poor programming when using an Object Oriented programming language. So I decided I wanted to extend (in Java-speak; most of my programming background is in Java) the in-built Image object. The new object's src variable will lead to an image of the type of flake it is. (I want to be able to have more variance in images than a simple dot.) The new object will have a function that will allow it to move. A separate, unrelated function will control when each flakes move. I did some more research and read about prototyping on JavaScript Kit and here, but I still cant seem to get this to work. JS Lint says it's bug-free, but Firefox says "move()" is an invalid function. I am presuming the problem lies in my inability to fully grasp how to extend objects in JavaScript. Code: <html>
<head>
<script type="text/javascript">
Image.prototype.dFlake=dotFlake;
function dotFlake(xLocation,yLocation){
this.src = "simpleDotFlake.png";
this.x = xLocation;
this.y = yLocation;
}
dotFlake.prototype.move = fall;
function fall(){ // ^^ Belongs to dotFlake class.
this.style.position="absolute";
this.style.top = this.y;
this.style.left = this.x;
this.y= this.y + 1; // Falling is constant.
if (Math.random() > 0.5){ // Random direction, though.
this.x = this.x + 1;
} else{
this.x = this.x - 1;
}
}
function snow(flakes){ // Allows addition of different flakes later.
for (i in flakes){
i.move();
}
timer = setTimeout("snow()",1);
}
function startSnow(){
basicFlakes = new Array(new dotFlake(0,0));
snow(basicFlakes);
}
</script>
</head>
<body onload="startSnow()">
<h1>This is test text.</h1>
<img id="basicFlake" src="./simpleDotFlake.png" width="10" height="10" />
</body>
</html>
Any and all input is much appreciated. Thank you! Hi all, I was under the impression that I and object/associative array could have other objects as the keys for properties. That is, I should be able to set myObject[anotherObject] = 1. However, while this seems to work at first glance, any new object I set as a property key overwrites the first one. Here is the result of me testing in my Chrome console: Code: > var obj1 = new Object();
> var obj1.someProperty = "test"
"test"
> var obj2 = new Object();
> obj2.someOtherProperty = "test2"
"test2"
> obj1 == obj2
false
> obj1 === obj2 // the two objects I created are definitely not the same
false
> x = {}
> x[obj1] = 0 // set the two objs as property keys on x
0
> x[obj2] = 1
1
> x[obj1]
1 // blargh! x.obj2 overwrote x.obj1!
Any idea if this is possible, and if I'm just messing up with something dumb? Probably a noob question but I'm to the point where I need suggestions. I am trying to make an object that adds more objects to the page onclick. For example, I have an image (lets say its a plus sign) that I want users to click to add a new predesignated image (lets say its an image that the user can label with text) to the page. I want the user to be able to create a page/list full of user labeled images. Thanks. I have an array of objects that I would like to sort through and "join" objects that are the same. And if they are the same, I need to sum up the number value given for those two items. So I guess Im sorting through and maybe even recreating this array to get rid of duplicates while I tally quantities. Please see the screenshot of my array of objects to help understand better. The highlighted 'sPSPN' would indicate that it is a duplicate item and its 'fUnits' need to be totalled. in the end I would have a total of 3 objects, because 'sPSPN'= BT-221-44 would now be only one object with 'fUnits' = 35. Thanks! Can somebody please link me to a good guide or tutorial for prototypes? Thanks Hey, I am using prototypes (library) ajax methods and one of them is properties. I am passing in the name value pairs: var itemFilter = "MajorCat: Shoes", parameters: { q : qry ,fq: itemFilter }, But when I request, it gives me this in the url: MajorCat%3AShoes That won't work, the search application on the backend doesn't filter properly because of the "%3A" instead of ":". When I manually pass in via the url: MajorCat: Shoes (at the end of the query) it works. So, that ":" is getting encoded. How do I get that IN the hash and make sure the request is unencoded when it goes out? thanks Hi, every time I try and alert: [ { number:0, secondnumber:0 }, { number:2, secondnumber:1 }, { number:1, secondnumber:2 } ] it just shows [object object], [object object], [object object]. Why is this and what can I do to make the record be shown as it is above in an alert? Thanks. I can't get any info from Firebug except that one line, uncaught exception [object Object]. The code fully worked, then I needed to make it dynamically create Sortables from the scriptaculous library based on how many X were in a table in my database, which I've done, and I'm thinking it may be a simple slight parse error of some type, I'm not too good with Javascript, because now my script barely works. I've double checked the script's source code, the PHP variables are exactly what they should be. Code: print<<<HERE
Sortable.create('sortlist$box', { tag: 'img', overlap:'horizontal',constraint:false, containment: $list, dropOnEmpty: true,
onChange: function(item) {
var list = Sortable.options(item).element;
if(changeEffect) changeEffect.cancel();
changeEffect = new Effect.Highlight('changeNotification', {restoreColor:"transparent" });
},
onDrop: function(item) {
var thing=Sortable.options(item).element.identify();
var anchors = document.getElementById(thing).childNodes.length-2;
if(anchors > 20){
alert('This box had 20 creatures in it already, your last action has not been saved.');
window.location.reload();
}
else{
new Ajax.Request("saveImageOrder.php", {
method: "post",
parameters: { data: Sortable.serialize("sortlist$box") }
});
}
}
});
HERE;
$box++;
}
?>
});
</script>
if you solve this I'll send ya $10 via paypal I created a method for displaying an object's properties: Code: renderfunction = false;
function showProperty (object, property)
{
document.write ('<td class="type">' + (typeof object[property]) + '</td>'
+ '<td class="name">' + property + '</td>');
document.writeln('<td class="value">' +
(
(typeof object[property] != 'function')
? object[property]
:(
(property != 'showProperties')
? (
renderfunction
? object[property]()
: ('<span class="self">NOT RENDERED</span>')
)
: ('<span class="self">THIS</span>')
)
)
+ '</td>');
document.writeln('<td class="hasOwnProperty" >'
+ (
object.hasOwnProperty(property)
? "Local"
: "Inherited"
)
+ '</td>');
if (typeof object[property] == 'function')
{
document.writeln ('<td class="function">' + object[property] + '</td>');
}
else
{
document.writeln ('<td class="function"> </td>');
}
}
As long as renderfunction = false, the object is fine coming out of this function. However, if I change renderfunction to true, all my properties become undefined. Why isn't this working as I expect it to? How should I fix it? Thanks in advance, -Brian. I'm writing a program that involves a network of interconnected nodes (or simply objects in my example below). It depends on being able to access properties of an object's linked objects (a bit oddly worded, sorry)... Problem is I'm not sure how to properly access those properties... see below please. <script> //This is an example of a problem im having in my own code... //I want to access the name of the object within the links array wintin the object... var objA = {name: "Object A", links: [objB, objC]}; var objB = {name: "Object B", links: [objC, objD, objE]}; var objC = {name: "Object C", links: [objB]}; var objD = {name: "Object D", links: [objE]}; var objE = {name: "Object E", links: [objD]}; //ex: I want to access the name of Object A's first link... console.log(objA.links[0].name); </script> I'm hoping to get "Object B"... But instead I get: TypeError: Result of expression 'objA.links[0]' [undefined] is not an object. Is there another way around this? Any thoughts are appreciated. Hello together! I generate html code with jsp. In that jsp there a several framesets and frames. And yes i know, frames are not really up to date but it's an old program and i have to deal with it now. Anyway, in the top frameset i have an onload attribute like onload="load()". In the function load i want to access the Element.prototype object. But unfortunately typeof Element gives me "undefined". So i looked a little deeper and found that window.toString() gives me "[object]" and not as expected "[object window]" so somehow my window doesn't know that its construcor is Window. window.construcor is "undefined" as well. And i don't have access to the Element object. I really don't know where the error could be. When the page is loaded and i access the same window over the console, then everything is right. But in my function a can't get access to the objects i need. I also don't know what part of the code could be useful to post here, but maybe someone had a similar problem before? i should say that this problem only occurs in IE8. In IE9 it works perfectly. Has anyone any idea?? Hi all, I'm stumped on finding a way in javascript to create an object factory whose instances are also object factories. In short I want something like that below, but no joy ... any clues? Code: function createClass () {
return new createClass()
function createClass() {
return new createInstance ()
function createInstance () {
//Default properties, values and methods which might later be extended
}
}
}
var createDoor = createClass();
var door1 = createDoor();
var door2 = createDoor();
var createChair = createClass();
var chair1 = createChair ();
var chair2 = createChair ();
Ignore post (if mod, please delete)
Quote: menu: function( a, b ) { $( b ).observe( 'click', function( event ) { event.stop(); if( $( a ).visible() ) { $( a ).hide(); $( b ).removeClassName( 'selected' ); document.stopObserving( 'click' ); } else { $( a ).show(); $( b ).addClassName( 'selected' ); document.observe( 'click', function( e ) { if( e.target.id != a && e.target.id != b && !Element.descendantOf( e.target, $( a ) ) ) { $( a ).hide(); $( b ).removeClassName( 'selected' ); document.stopObserving( 'click' ); } }); } }); $$( '#' + b + ' > a' ).each( function( element ) { element.observe( 'click', function( event ) { $( a ).hide(); $( b ).removeClassName( 'selected' ); document.stopObserving( 'click' ); }); }); } This work's perfrect accept when i use it with others on the menu it leaves the other ones open, how do i get it to close the open one when i open a new menu.. Thanks. Hello. Is there any way to get the variable name of an object from inside the object? E.g. PHP Code: function Bla(){ this.write = function(){ document.write(<objectname>); } } obj1 = new Bla(); obj1.write(); //Outputs obj1 Here is my script: PHP Code: function myTimer(seconds, obj){ this.seconds = seconds; this.obj = obj; this.startTimer = function(){ if(this.seconds>0){ this.seconds--; this.obj.innerHTML = this.seconds; this.timer = setTimeout("Timer.start()",1000); } } } Timer = new Timer(10, obj); Timer.startTimer(); Now the problem is that the variable that contains the object must be named "Timer". This way I cannot create new timer objects with different variable names I have tried: this.timer = setTimeout("this.start()",1000); but it doesn't work. That's why it would be good to detect the variable name and instead use something like this: this.timer = setTimeout(varname+".start()",1000); I would rather not have to pass the variable name through a parameter like this: Timer1 = new Timer(10, obj, "Timer1"); Thanks in advance. function($) { $.fn.superfish = function(op){ var sf = $.fn.superfish, c = sf.c, } So I see the '.superfish' method being added to the object '$.fn'. I find it interesting that the first order of business is to declare 'sf' and stuff in to it some value '$.fn.superfish' which I do not fully understand. Also the statement c=sf.c How can 'c' be set to equal 'sf.c' when no 'sf.c' has been declared yet? Thanks! Is it possible to create an array of objects? I require a two dimensional array of objects. Thanks! Good day, I have the following code: Code: var img = new Image(); img.myProperty = 'something'; I've tried Image.prototype.myProperty and a few other things. It seems IE just doesn't want me extending the Image object. Is there a known work-around? Thanks I am able to do the following; Code: alert(myObject.Income.EESA.Name); However I'm looking at Code: alert(myObject.Income[0].Name); Or even better, not the full name, just "EESA". I need to loop through as you can see at the end of this script what I'm working on. Code: <script type="text/javascript">
var EESARate = 289.3;
var DLARate = 111.20;
var CARate = 61.35;
var SkyCost = 54.75;
var PerfectHomeCost = 28.17;
var CreditExpertCost = 14.99;
var UnitedUtilitiesCost = 8.13;
var BTCost = 57.18;
var AdobeCCCost = 46.88;
var TVLicenceCost = 6.06;
var GasCost = 10.00;
var ElectricCost = 20.0;
var ServerPackageCost = 9.99;
var USDValue = 123; //Fetch the value
var myObject = {
"Income": {
"EESA": {
"Name": "Enhanced Employment and Support Allowance",
"Amount": {
"GBP": EESARate,
"USD": EESARate * USDValue
},
"Frequency": {
"When": "14",
"Next": "30/10/2014"
},
"Description": "",
},
"DLA": {
"Name": "Disibility Living Allowance",
"Amount": {
"GBP": DLARate,
"USD": DLARate * USDValue
},
"Frequency": {
"When": "7",
"Next": "Wednesday"
},
"Description": "",
},
"CA": {
"Name": "Carers Allowance",
"Amount": {
"GBP": CARate,
"USD": CARate * USDValue
},
"Frequency": {
"When": "7",
"Next": "Saturday"
},
"Description": "",
},
},
"Bills": {
"Sky": {
"Name": "Sky",
"Amount": {
"GBP": SkyCost,
"USD": SkyCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
"PerfectHome": {
"Name": "Sky",
"Amount": {
"GBP": PerfectHomeCost,
"USD": PerfectHomeCost * USDValue
},
"Frequency": {
"When": "7",
"Next": "Wednesday"
},
"Description": "",
},
"CreditExpert": {
"Name": "Experian Credit Expert",
"Amount": {
"GBP": CreditExpertCost,
"USD": CreditExpertCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
"UnitedUtilities": {
"Name": "United utilities",
"Amount": {
"GBP": UnitedUtilitiesCost,
"USD": UnitedUtilitiesCost * USDValue
},
"Frequency": {
"When": "7",
"Next": "Wednesday"
},
"Description": "",
},
"BT": {
"Name": "British Telecomunications",
"Amount": {
"GBP": BTCost,
"USD": BTCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
"AdobeCC": {
"Name": "Adobe Creative Cloud Suite",
"Amount": {
"GBP": AdobeCCCost,
"USD": AdobeCCCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
"TVLicence": {
"Name": "Television Licence",
"Amount": {
"GBP": TVLicenceCost,
"USD": TVLicenceCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
"Gas": {
"Name": "Eon Gas",
"Amount": {
"GBP": GasCost,
"USD": GasCost * USDValue
},
"Frequency": {
"When": "7",
"Next": "Wednesday"
},
"Description": "",
},
"Electric": {
"Name": "Eon Electric",
"Amount": {
"GBP": ElectricCost,
"USD": ElectricCost * USDValue
},
"Frequency": {
"When": "7",
"Next": "Wednesday"
},
"Description": "",
},
"ServerPackage": {
"Name": "1&1 Unlimited Plus (12 mo. term)",
"Amount": {
"GBP": ServerPackageCost,
"USD": ServerPackageCost * USDValue
},
"Frequency": {
"When": "30",
"Next": "XX/XX/XX"
},
"Description": "",
},
},
};
var IncomeTotal = 0;
for (var k in myObject.Income) {
if (myObject.Income.hasOwnProperty(k)) {
++IncomeTotal;
}
}
alert(myObject.Income.EESA.Name);
document.write('<table>')
for(i = 0; i < IncomeTotal; i++){
document.write('<tr>')
document.write('<td>row ' + (i+1) + ', column 0</td>')
document.write('</tr>')
}
document.write('</table>')
var TotalBills = 0;
for (var k in myObject.Bills) {
if (myObject.Bills.hasOwnProperty(k)) {
++TotalBills;
}
}
//alert(TotalBills);
</script>
I'm having a spot of trouble in making my functions work and my book seems to be pure rubbish. I'm sure that the error is purely syntax, although it may be something more. Code: <script type="text/javascript" src="flowers.js"></script>
<script type="text/javascript">
function pageSetup() {
var today = new Date(); // this creates a date object with today's date
var banner = displayBanner(today); // *should* call the displayBanner function
var days = calcDaysToSale(today); // *should* call the function using today's date
document.sale.saleMessage.value = days; // *should* set the value to days.
// Obviously none of it works.
}
</script>
This is the code working with the script contained in the html file. I'll post the full page at the bottom. The following code is the JavaScript code. The first function isn't made to provide full functionality at the moment, I'm trying to get the rest of it working. Code: function displayBanner(currentDate) {
if (currentDate.getMonth() == 2)
imgSrc = "winterLogo";
return ("<img src='" + imgSrc + ".gif'>");
}
function calcDaysToSale(currentDate) {
var saleDay = new Date();
saleDay.setDate(15); // sets the sale date to the 15th of the current month
// Subtracts the days remaining until the sale.
// If the number is negative, the sale is over.
var Days = saleDay.getDate()-currentDate.getDate();
if (Days < 0) {
return "The sale has ended.";
}
else {
return Days;
}
}
I have tried to Google the problem and I have also tried to look it up in my book. I simply don't know the right terms to Google, and as I said the book is rubbish. I don't know why the Code: document.sale.saleMessage.value = days; doesn't work for this. Oh well, I'll learn quickly I suppose. Here is the full HTML code: Code: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Carol's Flowers</title>
<link href="flowers.css" rel="stylesheet" type="text/css" />
<script type="text/javascript" src="flowers.js"></script>
<script type="text/javascript">
function pageSetup() {
var today = new Date(); // this creates a date object with today's date
var banner = displayBanner(today); // *should* call the displayBanner function
var days = calcDaysToSale(today); // *should* call the function using today's date
document.sale.saleMessage.value = days; // *should* set the value to days.
// Obviously none of it works.
}
</script>
</head>
<body class="oneColLiqCtrHdr">
<div id="container">
<div id="header">
<p><img name="myBanner" src="banner" id="myBanner" alt="Carol's Flowers" />
<!-- end #header -->
</p>
<div id="links"><a href="#">Home</a> | <a href="#">General Arrangements</a> | <a href="#">Seasonal Designs</a> | <a href="#">Custom Orders</a> | <a href="#">Location</a></div>
</div>
<div id="mainContent">
<table id="mainTable">
<tr>
<td width="201"><h1><img src="Flowers.JPG" alt="Random Flowers" width="200" height="255" /></h1></td>
<td width="687">
<p>Here at Carol's Flowers, we believe that there is a perfect floral arrangment for every occasion! Take a look around and see if there is anything you like. If we don't already have it, then we will create it for you!</p></td>
</script>
</tr>
</table>
<!-- end #mainContent --></div>
<div id="footer">
<p> <form name="sale" id="sale">
Days Until Mid Month Madness Sale :
<input type="text" name="saleMessage" id="saleMessage" /></form></p>
<!-- end #footer --></div>
<!-- end #container --></div>
<!-- I am trying to run the script here -->
<script type="text/javascript">
pageSetup();
</script>
</body>
</html>
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