Events - Convert Some Procedural Code To Be More Object Oriented
Jul 9, 2009
I'm trying to convert some Procedural code to be more Object Oriented and I'm stuck...
The page is really simple:
It's just a big picture w/ a caption under it, and a few thumbnail pics off to the side, that when clicked, replace the big picture as well as swap out the caption for a new one.
In the code (external JS file):
I've got 2 arrays:
One that holds the thumbnail image file URLs, and the other that holds the captions.
And a function:
I've created an object prototype that I can instantiate in order to:
1.) create the event: do the actual swapping of the thumbnail, and the changing of the caption.
2.) and attach that event to the thumbnail's link onclick event handler.
The code below is the closest I've come to making it work. The problem is that when I click any of the thumbnail links it only executes the last event instead of the one that corresponds to the link that was just clicked. Hopefully someone can take a look at my code and let me know what I'm doing wrong.
Simplified version of the code:
The x,y,z variable assignments are only in the window.onload function for the sake of clarity, but the event object instantiation block has to be in there for anything to work at all.
I know that the event0,event1,event2 objects work, and are attached to the onclick handler because they will swap the last thumbnail and caption when I click any of the thumbnail links. Of course that's the problem now... any click only activates the last event. It's like it attached the last event to all the onclick event handlers.
In fact, if I only create the event0 object, it works like it's supposed to... but when I create the event1 object, it does what it's supposed to and it takes over for event0. Creating event2 makes it take over for all of them. Each subsequent event# object seems to attach its own addy[ ] and caption[ ] to each previous x[ ] link.
I was writing my classes in an old fashion until today when I came across a new design pattern. Javascript is not an established OOP like C++ or Java. It doesn't have any easy way to create classes and to make private/public methods or properties as well as class-constructor. But it could be done in many ways.
My old way of OO design in Javascript was like following:
Code:
Those who were trying to write constructor and access public vars from private or vice versa, you would have probably faced some minor difficulties. But it was doable.
Now, the challenge is how can we make things cleaner and better. Here's the procedure I came up with:
I just released javascript lib that really helps to develop robust and clear js-scenarios following the OOP directions. The library is compatible with wide range of browsers on different platforms, including Netscape 4.x, Netscape 6.x, Netscape 7.x, Opera 6, Opera 7, Mozilla 1.0, IE 4, IE 5, IE 6.
I will be the first to admit, I don't know much about JS and am just starting to wrap my mind around object oriented js. I have this small bit of code that has been giving me problems for days.
playlistItems[numItems-1] = soundManager.createSound({ id : songId, url : $(this).attr('href'), whileloading : player.whileloading, onfinish: next });
"next" is a function on the same object that playlistItems is defined on, but it doesn't ever seem to fire. I tried this.next as well, but it just gives me a runtime error....
The problems with the setTimeout and setInterval functions provided in Javascript are twofold. First, you can't call a local object method without losing your scope, and second, you can't pass objects to the function, since the function call is implemented as a string.
The Timer class solves these difficulties by employing a static array to store the parent object and function arguments until the function is called.
This class is provided as-is and pro bono, so go ahead and muck with it if you see things that could be done better.
Thanks to WA for giving me the idea for this (albeit indirectly)!
Updated 4/18/2003: Footprint decreased, minor code improvements. Updated 5/3/2003: Minor comment clarification; no code changes. Updated 5/10/2003: Minor code improvements. // The constructor should be called with // the parent object (optional, defaults to window).
function Timer(){ this.obj = (arguments.length)?arguments[0]:window; return this; }
// The set functions should be called with: // - The name of the object method (as a string) (required) // - The millisecond delay (required) // - Any number of extra arguments, which will all be // passed to the method when it is evaluated.
Timer.prototype.setInterval = function(func, msec){ var i = Timer.getNew(); var t = Timer.buildCall(this.obj, i, arguments); Timer.set[i].timer = window.setInterval(t,msec); return i; } Timer.prototype.setTimeout = function(func, msec){ var i = Timer.getNew(); Timer.buildCall(this.obj, i, arguments); Timer.set[i].timer = window.setTimeout("Timer.callOnce("+i+");",msec); return i; }
// The clear functions should be called with // the return value from the equivalent set function.
I am trying to make a round corners script in object oriented programming method. This is purely for learning purposes.
The script is no where near complete but I am already having problems with it.
I am trying out the techniques described in 'David Flanagan ' text book 'JavaScript: The Definitive Guide, 5th Edition'
This code is called from html page which once working will place a round container around element
The selector parameter in Custom_rounded_container function is defined because only the else part of the if statement in Custom_rounded_container is executing. I put this in because few people at other forums thought the problem was because of the selector parameter being undefined.
Trying to figure out OO programming for JavaScript and I'm totally lost.
Here's what I'm trying to do:
I'm posting search data to a PHP form to run a query on a database.
The structure is sort of like this:
So I'm thinking I need to create search objects or arrays. Initially, I thought I could do something like this:
Code:
This doesn't seem to work. It says object not defined whenever I try to do something.
I've also tried creating a JSON object like this:
Code:
This will allow me retrieve the data like I want to:
Code:
The problem is I can't figure out how to add data to the JSON object without manually typing it in. I need to be able to loop through form elements on my HTML page and set them to these variables. I'm using jQuery and doing something like this:
I've been trying to create a 'loading page' for a from. When a user submitts a form, a loading animation is displayed on the page. Then I have javascript connecting to a url on my server that generates a dynamic file and returns it from memory. My problem is that I can display the text from this new file, but what I want to do is prompt the user to save the file locally. Is there a way to make this sort of conversion in javascript?
I have anonymous function "xhr.onreadystatechange = function() {}" in the method "this.update" of an object that receives 2 arrays through AJAX. I need these 2 arrays to be assigned to this.images and this.folders, respectively, through this anonymous function. I try to use "var self" technique, but it doesn't work.
How do I explain this? I am grabbing several elements from my document and placing them in an array, using jQuery. When I test the Code: typeof this item, it returns as an Object, not an Array, which is problematic for IE. Firefox seems not to have an issue with Code: Object.length , but IE won't have any of that, so I need Code: Array.length or do I? In the end, I just want IE to know how many keys are in the Array/Object...
In addition to fetching JSON you might want to POST it back to the server, but there is no postJSON method. You cannot use the generic ajax method, either. What is missing is the complement of "eval" to turn a JavaScript object in to JSON. The JSON.stringify function from www.json.org (see json2.js in JavaScript section) does the trick, but it would be nice if jQuery incorporated that out of the box, to save some hunting time.
Using the jquery ajax method to set the "type" to "json" and the "content-type" to "application/json" send and recieve JSON, but you must use JSON.stringify to convert your outgoing object to JSON. P.S.. a lot of forgiving parsers have resulted in a lot of articles on JSON being wrong. would I like to mention that here. Property names are JSON strings. JSON strings have double quotes. Therefore, property names have to be surrounded with double quotes. Single quotes are not JSON strings and not legal (JSON is not JavaScript).
I think this is a problem converting (what is assumed to be) a string to numeric. or something like that.
rvs = s[i][j] * k; Firefox Error Console says: Uncaught exception: TypeError: Cannot convert 's[0]' to object rvs is just a (temporary, holding) variable. s is a [3][6] array on numeric values. i, j and k all happen to be zero. [Code]..
I'm new to jQuery but pretty familiar with JavaScript. I would like to convert the code below to a function that can be used like "$("#member-feedback li ").rotateElements()". I've looked at some examples, but I'm not sure where to start.
I'm having a hard time figuring out how to refer to an object while inside a jquery event function. In the following example, "this" at first is referenced as #myDiv. But inside the draggable event, "this" refers to something else. I am not sure what it is referring to, but how do I reference the original object (Human) from within this event?
var Person = new Human("#myDiv", "my data"); function Human(element, myName) { this.name = myName;
