Develop Reference

How to load the contents of a file and insert a variable in it using Javascript?

I'm adding some html to a div using the following jQuery method:
$('#pageTabContent').append($('\
<div class="tab-pane" id="'+ticketId+'">\
And a whole lot more html here..
</div>'));
This works fine, but because I've got way too much html in my javascript I want to move that to a separate file. The problem is that I also need to insert the ticketId in the html. Is there a way using Javascript/jQuery to load the html from a separate file, but still insert the ticketId in it?
[EDIT] Please note that the ticketId is different for every time this piece of code is used. I will be used multiple times within one page load, so I cannot load the ticketId in the html using php. I has to be done client side.
All tips are welcome!

For that specific example, it's pretty straightforward:
$.get("/path/to/file.html", function(html) {
var newStuff = $(html);
newStuff.find("div.tab-pane:first").attr("id", ticketId);
newStuff.appendTo("#pageTabContent");
});
You can generalize that a bit, the basic concept is: 1. Load the HTML, 2. Use jQuery to create DOM elements from it, 3. Use jQuery to find the element in question and modify it, 4. Add to the element.
Another approach is to use some form of templating, either a templating plugin or just DIY:
$.get("/path/to/file.html", function(html) {
html = html.replace("{{ticketId}}", ticketId);
$("#pageTabContent").append(html);
});
Again, there are plugins and templating systems to do that for you, which would offer various features over doing your own.

I generally recommend avoiding dynamic html generation in javascript.
There are several good template based frameworks out there. One I like to use in KnockoutJS http://knockoutjs.com/
Another benefit of this approach is change tracking between your model and your html elements.

Including a custom js file on rails_admin dashboard

I am trying to include a custom js for a custom field that depends on a google maps control, I don't want to mix html and js on a partial file, however, up to now, it appears to be the way to go.
I have checked on the wiki and the only reference about including a custom js is here but it doesn't work.
I only want to be able to organize my javascripts as usual (at assets/javascripts/) and be able to interact with my rails_admin form views. Anyone has any idea on how this should be handled?

To restate: It sounds like you are trying to keep javascript code out of view (html/erb) files.
I can recommend one way you may wish to try.
If you look at the assets/javascript directory you can see the generated javascript files that are created per controller when you are scaffolding a resource.
These files are great for keeping all the code related to the controller context in. there is another file named application.js which is great to keep global javascript routines in.
If you put tags/fields on the elements which you wish to select to bind a javascript method to you are able to keep the methods focused on finding and binding fields sharing the tag.
example:
field you wish to interact with:
Blah
your_controller_name.js:
using jquery you should be able to select the span by the data tag ( you could stored extra infor. you can then also bind methods to the span.
$("span[data-interesting='hi there']").click(function() { console.log('someone clicked the span'); })
You could use a selector that is more general and do something useful to all the matching items.
Good luck!
James.

How to let JavaScript know where I am on the site?

I have a single template file which renders pages that look very similar, but behave a bit different. I have a header and a few text boxes, which are filled by the template language, and there is a canvas, whose content actually differentiates the pages. It basically comes down to calling a different JavaScript function based on the page I am on, and I can't really think of an elegant (!) way to do that.
I have a single JavaScript file that uses jQuery's document ready callback to add interactivity to the site, and also to do the drawing in the canvas. For that, I have to call a specific drawing function based on which page I am on, but I don't know it at that point.
This is certainly not impossible, I can in fact think of several different solutions, but don't really like any of these. The script file is not run through a template engine, so I can't employ any server-side logic there. I could parse the URL in the script, but this sounds like a hack to me. I could also set a variable in a script block within the template file, set a hidden field's value or something like that, but I don't think this logic belongs into the template either.
So how is this usually done?

You can give the <body> tag a "class" value, and your JavaScript code can use that (and other similar cues) to know what sorts of behaviors to add.
For example, your code could do something like:
if ($('body').hasClass('image-gallery')) {
// ... initialize image gallery code ...
}
if ($('body').hasClass('shopping-cart-summary')) {
// ... whatever ...
}
Of course it doesn't have to be just the <body> tag. Your <canvas> could also get a "class" value (and/or "data-foo" attributes) to convey information to your code.

You can embed any JavaScript you want on to a web page, built with the same server-side logic you would build the page with. So you can set global variables or (preferably) invoke functions from your .js files with parameters that contain page-specific logic. Just supply the scripts between <script> tags.

It is not clear if you want to find the page you are on, or the location in the DOM of a given page. For the former, use location.href, or location.pathname to avoid the parsing.

Custom View Engine to solve the Javascript/PartialView Issue?

I have seen many questions raised around PartialViews and Javascript: the problem is a PartialView that requires Javascript, e.g. a view that renders a jqGrid:
The partial View needs a <div id="myGrid"></div>
and then some script:
<script>
$(document).ready(function(){
$('#myGrid').jqGrid( { // config params go here
});
}
</script>
The issue is how to include the PartialView without littering the page with inline tags and multiple $(document).ready tags.
We would also like to club the results from multiple RenderPartial calls into a single document.Ready() call.
And lastly we have the issue of the Javascript library files such as JQuery and JQGrid.js which should ideally be included at the bottom of the page (right before the $.ready block) and ideally only included when the appropriate PartialViews are used on the page.
In scouring the WWW it does not appear that anyone has solved this issue. A potential way might be to implement a custom View Engine. I was wondering if anyone had any alternative suggestions I may have missed?

This is a good question and it is something my team struggled with when JQuery was first released. One colleague wrote a page base class that combined all of the document ready calls into one, but it was a complete waste of time and our client's money.
There is no need to combine the $(document).ready() calls into one as they will all be called, one after the other in the order that they appear on the page. this is due to the multi-cast delegate nature of the method and it won't have a significant affect on performance. You might find your page slightly more maintainable, but maintainability is seldom an issue with jQuery as it has such concise syntax.
Could you expand on the reasons for wanting to combine them? I find a lot of developers are perfectionists and want their markup to be absolutely perfect. Rather, I find that when it is good enough for the client, when it performs adequately and displays properly, then my time is better spent delivering the next requirement. I have wasted a lot of time in the past formatting HTML that no-one will ever look at.
Any script that you want to appear at the bottom of the page should go inside the ClientScriptManager.RegisterStartupScript Method as it renders at the bottom of the page.
http://msdn.microsoft.com/en-us/library/z9h4dk8y.aspx
Edit Just noticed that your question was specific to ASP.NET MVC. My answer is more of an ASP.NET answer but in terms of the rendered html, most of my comments are still relevant. Multiple document.ready functions are not a problem.
The standard jQuery approach is to write a single script that will add behaviour to multiple elements. So, add a class to the divs that you want to contain a grid and call a function on each one:
<script language="text/javascript">
$(document).ready(function(){
$('.myGridClass').each(function(){
$(this).jqGrid( {
// config params can be determined from
//attributes added to the div element
var url = $(this).attr("data-url");
});
});
}
</script>
You only need to add this script once on your page and in your partial views you just have:
<div class="myGridClass" data-url="http://whatever-url-to-be-used"></div>
Notice the data-url attribute. This is HTML5 syntax, which will fail HTML 4 validation. It will still work in HTML 4 browsers. It only matters if you have to run your pages through html validators. And I can see you already know about HTML5

Not pretty but as regards your last point can you not send the appropriate tags as a ViewData dictionary in the action that returns the partial?

What is the best way to organize unobtrusive JavaScript across multiple pages?

I love jQuery but am running into a problem with larger site and multiple pages. My problem is that each page has unique requirements and I need to know the best way to tell jQuery which pages to activate certain things. For example, some forms need the Validator plug-in and some don't, some tables use DataTables plug-in and some don't, etc.
Now I guess I could build complex logic (switch statements) into my application JavaScript file that fire different actions depending on what page they are on, but that just seems smelly. What is the Best Practice here?
UPDATE: There have been lots of good ideas on this question but not quite what I'm looking for. Let me rephrase the question in a more general way.
Currently I am using Rails and its Prototype helpers to build my AJAX components, but I want to move to UJS. How do I tell jQuery which links/buttons to make AJAX and which to avoid? And, given that I can differentiate the that are supposed to have AJAX, how do I give each link its own parameters (method, update, etc.) like I could with the helpers?
I mean besides building a huge page of specific jQuery selectors targeting each individual link/button. :)

jQuery plugins usually are activated upon DOM elements, for example:
$("#element").myPlugin();
If the element doesn't exist on the page, plugins usually behave safely by not activating the plugin.
If your plugin doesn't follow this structure I would suggest doing something like this:
if($("#element").length) $("#element").myPlugin();

A good practice is to have code that is required by all pages in one file and to have specific javascript files for pages that require specific functionality. It sounds as though this is what you are doing anyway, so we have a good basis to build upon.
There are numerous ways in which you could build in what pages need what files, but remember that in normal circumstances, javascript files are cached by the browser such that those files need only downloading once.
In light of this comment
Yes, but what if you have multiple
pages with the same DOM elements? For
example, my validator() plugin is set
up like $('form').validate(), but
sometimes I don't want it to act on
all the forms on the page, only some
of them. What do I do in this case?
I suggest coming up with a convention by which to label elements common across pages that require certain jQuery plugins "attached" to them. For example, if you have a <form> element on a number of different pages that requires a validator() plugin, but there is more than one <form> element on any one particular page (and not all <form> elements should have the validator() plugin), then I suggest using a CSS class to distinguish the <form> elements that do need the plugin.
<!-- HTML -->
<!-- need to apply plugin to this -->
<form class="validator"> ... </form>
<!-- but not to this -->
<form> ... </form>
<script type="text/javascript">
// jQuery Code (in a separate file)
$(function() {
$('form.validator').validator();
});
</script>
That way, the plugin will be applied only to those <form> elements matching the selector.
EDIT:
I'm not sure how the helpers in rails work, but you can pass data to an event handler in jQuery using the data parameter of the bind() method for any data that is not directly part of an <a> element itself (such as an attribute like href). If some of the links require AJAX, then it may make sense to label those with a CSS class and store the URL in the href for the element. Then in your jQuery code that can be used on any pages that have links that make requests through AJAX, you could do something like
<a class="ajax-link" href="/get/someData.php">Data retrieved through AJAX</a>
Standard link with no AJAX
<script type="text/javascript">
$('a.ajax-link').bind('click',ajaxRequest);
function ajaxRequest(e) {
e.preventDefault();
$.get(e.target.href, function(data) {
$('#loadDiv').html(data);
});
}
</script>
the link will work as per a normal link when a user has JavaScript disabled, but will make an AJAX request for data when JavaScript is enabled. I've used a named function here, ajaxRequest as it can make it easier to debug the script (and perhaps also reuse), but you could use an anonymous function if you prefer.

Found nice custom solution
http://topsecretproject.finitestatemachine.com/2010/04/how-to-organizing-javascript-in-ruby-on-rails/

One thing I always do is add an id to the body tag of each page, where the id is the name of the page (<body id="contact">). That makes both javascript and css selection very easy.
For example:
<!-- HTML -->
<!-- need to apply plugin to these forms -->
<form> ... </form> on the about.php page
<!-- but not to this -->
<form> ... </form> on the index.php page
<script type="text/javascript">
// jQuery Code (in a separate file)
$(function() {
$('body#about form').validator();
});
</script>

You could pass key value pairs to your main JavaScript module informing which plugins should be imported. This technique is used by scriptaculous.
<script type="text/javascript" src="scriptaculous.js?load=effects,dragdrop">
Another approach is to define in server side which media files are needed for each form/page, so the html can be rendered automatically with links to the scripts that are going to be used. Django has a good implementation of this technique:
class CalendarWidget(forms.TextInput):
class Media:
css = {
'all': ('pretty.css',)
}
js = ('animations.js', 'actions.js')