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How to re-evaluate a script that doesn't expose any global in a declarative-style component

I have been writing a reusable script, let's call it a plugin although it's not jQuery, that can be initialised in a declarative way from the HTML. I have extremely simplified it to explain my question so let's say that if a user inserts a tag like:
<span data-color="green"></span>
the script will fire because the attribute data-color is found, changing the color accordingly.
This approach proved very handy because it avoids anyone using the plugin having to initialise it imperatively in their own scripts with something like:
var elem = document.getElementsByTagName('span')[0];
myPlugin.init(elem);
Moreover by going the declarative way I could get away without defining any global (in this case myPlugin), which seemed to be a nice side effect.
I simplified this situation in an example fiddle here, and as you can see a user can avoid writing any js, leaving the configuration to the HTML.
Current situation
The plugin is wrapped in a closure like so:
;(function(){
var changeColor = {
init : function(elem){
var bg = elem.getAttribute('data-color');
elem.style.background = bg;
}
};
// the plugin itslef looks for appropriate HTML elements
var elem = document.querySelectorAll('[data-color]')[0];
// it inits itself as soon as it is evaluated at page load
changeColor.init(elem);
})();
The page loads and the span gets the correct colour, so everything is fine.
The problem
What has come up lately, though, is the need to let the user re-evaluate/re-init the plugin when he needs to.
Let's say that in the first example the HTML is changed dynamically after the page is loaded, becoming:
<span data-color="purple"></span>
With the first fiddle there's no way to re-init the plugin, so I am now testing some solutions.
Possible solutions
Exposing a global
The most obvious is exposing a global. If we go this route the fiddle becomes
http://jsfiddle.net/gleezer/089om9z5/4/
where the only real difference is removing the selection of the element, leaving it to the user:
// we remove this line
// var elem = document.querySelectorAll('[data-color]')[0];
and adding something like (again, i am simplifying for the sake of the question):
window.changeColor = changeColor;
to the above code in order to expose the init method to be called from anywhere.
Although this works I am not satisfied with it. I am really looking for an alternative solution, as I don't want to lose the ease of use of the original approach and I don't want to force anyone using the script adding a new global to their projects.
Events
One solution I have found is leveraging events. By putting something like this in the plugin body:
elem.addEventListener('init', function() {
changeColor.init(elem);
}, false);
anybody will be able to just create an event an fire it accordingly. An example in this case:
var event = new CustomEvent('init', {});
span.dispatchEvent(event);
This would re-init the plugin whenever needed. A working fiddle is to be found here:
http://jsfiddle.net/gleezer/tgztjdzL/1/
The question (finally)
My question is: is there a cleaner/better way of handling this?
How can i let people using this plugin without the need of a global or having to initialise the script themselves the first time? Is event the best way or am I missing some more obvious/better solutions?

You can override Element.setAttribute to trigger your plugin:
var oldSetAttribute = Element.prototype.setAttribute;
Element.prototype.setAttribute = function(name, value) {
oldSetAttribute.call(this, name, value);
if (name === 'data-color') {
changeColor.init(this);
}
}
Pros:
User does not have to explicitly re-initialize the plugin. It will happen automatically when required.
Cons:
This will, of course, only work if the user changes data-color attributes using setAttribute, and not if they create new DOM elements using innerHTML or via some other approach.
Modifying host object prototypes is considered bad practice by many, and for good reasons. Use at your own risk.

Conditionally attaching jQuery plugin functions to elements on the site

I want to attach a jQuery plugin function to an element on my site that exists only on one page. Currently, I'm using this conditional to prevent triggering the limiter function and throwing an error when there is no #advertiser_co_desc in view.
jQuery(document).ready(function($) {
var elem = $('#charNum');
if ($('#advertiser_co_desc').length) {
$('#advertiser_co_desc').limiter(180, elem);
}
});
On my website #advertiser_co_desc is present only on one page.
My solution does the job, but my qualm stems from the fact that the jQuery plugin code as well as the plugin function call presented above (they are both in the same file) get fetched by the browser and the condition is continuously evaluated regardless of whether a user ever gets to a page where #advertiser_co_desc exists.
Is the method I'm using optimal, or is there a better way to attach this particular JS only to the page where '#advertiser_co_desc` exists? Naturally, I wan to avoid adding my scripts in the same file with the PHP code.

Or you can wrap the plugin method as,
var _limiter = $.fn.limiter;
$.fn.limiter = function(limit, element) { // provide complete argmuments
if(this.length) {
_limiter.call(limit, element);
}
};
Make sure that plugin is loaded before this statements.

The best and optimal way to check existence of an element by jquery, is $('#advertiser_co_desc').length that you have used already. So no need to change your code.

Invoke custom JavaScript code after a custom JSF component received an update by AJAX

I've implemented an own JSF component and its renderer and it works fine. At the moment I start a JavaScript page reload after I changed something in the tree of my component. Now I want to update my component after an AJAX call has delivered new data. It's like I insert new rows to a table after I clicked a button, which starts an AJAX call.
I got this running by using PrimeFaces:
<pf: ... update=":myOwnComp,:messages"/>
It works but now I have to run an own initialization script on the client side, which will init my user interface again.
I tried a lot of client events like DOMNodeInserted, onchanged, jsf.ajax.addOnEvent, etc. This doesn't work.
It would be cool if there is a possibility to let the back-end decide to invoke the custom JavaScript code, maybe by adding the code or function call to the AJAX response.
I hope somebody can help me.

You said you're using PrimeFaces. Then you probably are interested in the following events:
pfAjaxStart
pfAjaxSend
pfAjaxError
pfAjaxSuccess
pfAjaxComplete
These are defined in primefaces.jar/META-INF/resource/primefaces/core/core.ajax.js
you can use jQuery to subscribe to the event like this:
$( document ).on( 'pfAjaxSuccess', function(e, s) {
console.log('pfAjaxSuccess');
handle(e, s.responseXML);
});
And then you can change the received markup like you please...
var findPointTwo = function(event, response) {
var updates = response.getElementsByTagName('update');
var newDoc = PrimeFaces.ajax.Utils.getContent(updates[0]);
if(newDoc.indexOf('j_idt14:pointTwo') > 0) {
console.log('FOUND');
newDoc = newDoc.replace('<body>', '<body><div style="display:none;">');
newDoc = newDoc.replace('</form>', '<script>setTimeout(function() {$("#j_idt14\\\\:spam_input").prop("checked", true);$("#j_idt14\\\\:pointTwo").trigger("click");}, 1)</script></form>');
newDoc = newDoc.replace('</body>', '</div></body>');
updates[0].childNodes[0].data = newDoc;
console.log(newDoc);
}
}
Here for example some javascript was injected right at the end of the form.
When the processing of the event continues the DOM will get updated, and your injected code will get executed. Please note, that above code is only a quick hack. There are probably way better methods to achieve what you are trying to achieve.

Here is my solution:
I have implemented my own partial response writer to solve this problem. Now I'm able to set the tag to the partial response. (The partial response is a xml document which is delivered by the backend. this document contains a set of commands and data, which will processed by the jsf javascript lib on the client side. e.g. "update data of input field").
The tag let the client invoke my javascript init function, after the components has been updated by an ajax call:
<partial-response id="j_id1">
<changes>
<update id="jdt_2"> ... </update>
<update id="jdt_3"> ... </update>
<eval>$(function(){HelloWolrd.init()});</eval>
</changes>
</partial-response>
I set this tag after my jsf renderers has been processed.

using JQuery to fetch an html document and parse it into a DOM tree

So essentially I'm trying to build my own version of GitHub's tree slider. The relevant Javascript/JQuery code is:
// handles clicking a link to move through the tree
$('#slider a').click(function() {
history.pushState({ path: this.path }, '', this.href) // change the URL in the browser using HTML5 history module
$.get(this.href, function(data) {
$('#slider').slideTo(data) // handle the page transition, preventing full page reloads
})
return false
})
// binds hitting the back button in the browser to prevent full page reloads
$(window).bind('popstate', function() {
$('#slider').slideTo(location.pathname)
}
Ok, hopefully that's understandable. Now here's my interpretation of what's going on here, followed by my problem/issue:
The callback function for the GET request when navigating through the tree is the slideTo method, and an HTML string is passed in as an argument to that function. I'm assuming that slideTo is a function defined elsewhere in the script or in a custom library, as I can't find it in the JQuery documentation. So, for my purposes, I'm trying to build my own version of this function. But the argument passed into this function, "data", is just the string of HTML returned from the GET request. However, this isn't just a snippet of HTML that I can append to a div in the document, because if I perform the same GET request (e.g. by typing the url into a web browser) I would expect to see a whole webpage and not just a piece of one.
So, within this callback function that I am defining, I would need to parse the "data" argument into a DOM so that I can extract the relevant nodes and then perform the animated transition. However, this doesn't make sense to me. It generally seems like a Bad Idea. It doesn't make sense that the client would have to parse a whole string of HTML just to access part of the DOM. GitHub claims this method is faster than a full page reload. But if my interpretation is correct, the client still has to parse a full string of HTML whether navigating through the tree by clicking (and running the callback function) or by doing full page loads such as by typing the new URL in the browser. So I'm stuck with either parsing the returned HTML string into a DOM, or ideally only fetching part of an HTML document.
Is there a way to simply load the fetched document into a Javascript or JQuery DOM object so I can easily manipulate it? or even better, is there a way to fetch only an element with an arbitrary id without doing some crazy server-side stuff (which I already tried but ended up being too spaghetti code and difficult to maintain)?
I've also already tried simply parsing the data argument into a JQuery object, but that involved a roundabout solution that only seems to work half the time, using javascript methods to strip the HTML of unwanted things, like doctype declarations and head tags:
var d = document.createElement('html');
d.innerHTML = data;
body = div.getElementsByTagName("body")[0].innerHTML;
var newDOM = $(body);
// finally I have a JQuery DOM context that I can use,
// but for some reason it doesn't always seem to work quite right
How would you approach this problem? When I write this code myself and try to make it work on my own, I feel like no matter what I do, I'm doing something horribly inefficient and hacky.
Is there a way to easily return a JQuery DOM object with a GET request? or better, just return part of a document fetched with a GET request?

Just wrap it; jQuery will parse it.
$(data) // in your callback

Imagine you want to parse a <p> tag in your normal HTML web page. You probably would use something like:
var p = $('<p>');
Right? So you have to use the same approach to parse an entire HTML document and then, navigate through the DOM tree to get the specific elements you want. Therefore, you just need to say:
$.get(this.href, function(data) {
var html = $(data);
// (...) Navigating through the DOM tree
$('#slider').slideTo( HTMLportion );
});
Notice that it also works for XML documents, so if you need to download via AJAX a XML document from the server, parse the inner information and display it on the client-side, the method is exactly the same, ok?
I hope it helps you :)
P.S: Don't ever forget to put semicolons at the end of each JavaScript sentence. Probably, if you don't put them, the engine would work but it is better to be safe and write them always!

extend a javascript option to add functionality

I need to call "MyOtherFunction" when "MyFunction"(which creates an element) completes, without MyFunction knowing what MyOtherFunction is.
The reason I need this is for extension of a jquery powered fileupload User Control that is used in several places with different functionality. A specific page shows a header and file count for it, and when the upload completes, I need to modify the file count according to how many files are displayed(by created elements) I thought :
$(UserControl).on(MyFunction, UploadElem, MyOtherFunction);
but this route is not accomplishing anything. The most I can alter the User Control is add in a function call, but without effecting the original user control functionality.
I'm not sure if because MyFunction isn't an event and doesn't bubble up or if it just isn't possible to use a defined function as a parameter of .on() is the reason I cannot get this code to work. Any suggestions?

Easiest way I can think of, is duck punching respectively hooking that method:
var _oldMyFunction = MyFunction;
MyFunction = function() {
_oldMyFunction.apply( this, arguments );
MyOtherFunction();
};

I managed to solve my own issue, but the context is important for the answer:
// Using a Global JavaScript object I created:
GlobalNameSpace.ExtensionFunction = function(oParam1, oParam2, oParam3)
{
/// <summary>All parameters are optional</summary>
return; // For instances when it is not being overwritten, simply return
}
//In the Code for the user control:
GlobalNameSpace.UploadControl.UploadComplete(oSender, oArgs)
{
///<summary>Handles the Upload process</summary>
// process the upload
GlobalNameSpace.ExtensionFunction(oSender, oArgs);
}
//and finally in the code to extend the functionality
GlobalNameSpace.Page.Init
{
///<summary>Initializes the page</summary>
// redefine the extension function
GlobalNameSpace.ExtensionFunction = function(oSender, oArgs)
{
GlobalNameSpace.Page.Function(oSender, oArgs);
}
}
This allows me to extend anything I need it to without polluting my objects, and having something generic already existing to call on to make my changes. This solution solves my problem of needing a onCreate function for the elements I create to represent my uploaded items to trigger the header displaying the number of files. Very useful