Develop Reference

html, js - how to limit elements "scope" - namespaces

During last perioud I've seen more and more often the following situation.
Developer A creates a feature. Let's say is an autocomplete input. Let's assume for simplicity that no framework is used, html and js are on the same file. The file would look like this (let's also asume jquery used - is less to type):
<!-- autocomplete something.html file -->
.........................................
<input id="autocomplete" type="text" />
<script type="text/javascript">
$('#autocomplete').change(function() {
// Do lots of things here -> ajax request, parsing, etc.
});
</script>
.........................................
Now developer B sees the feature and says "Oh, nice feature, I can use that in my section, I'll put one at the top, and one at the bottom - because page is long".
And he does an ajax call to get that html file (this is important, I'm talking about features loaded like this, not features rewritten for the other section) and includes it where he needs it.
Now... problem. The first autocomple works, the second doesn't (because is select by id).
A workaround would be to modify, and use a class. And everything is ok, unless someone else (or himself, or whatever) uses same class for a tottaly different thing.
This could all be avoided if you could the the script to use as a "scope" (I know it is not the correct phrasing, couldn't find any better) the file where it was declared on.
Note: This is a theoretical question. For each particular case a solution could be found, but defining some kind of namespaces for this scenarios would solve the whole class of problems.
How could that be achieved?

As long as you're accessing the DOM the only way I see would be to use the "old" inline event:
<!-- autocomplete something.html file -->
.........................................
<input onchange="autocomplete_change();" type="text" />
<script type="text/javascript">
function autocomplete_change() {
// Do lots of things here -> ajax request, parsing, etc.
};
</script>
...........
Now the function name cannot be used by Developer B.
But when accessing DOM some kind of restriction will always be there.
However when creating the input by Script you can bind the handler directly to the Element:
<script>
var input = $('<input type="text"/>');
input.change(function() {
// Do lots of things here -> ajax request, parsing, etc.
});
document.body.appendChild(input[0]);
</script>

kicking off ajax query to php mysql DB by use of onblur

I'm trying (and failing) to make an ajax process work when people leave a form input field. I need it to happen for each input field, of any type, on the form.
I'm trying to modify the following (which does work):
$("document").ready(function() {
$("#getcontent").click(getContent);
});
function getContent() {
$("#example").load("sampletextcontent.txt");
}
(there would be a button with id="getcontent" in the html, and a div with id="example" also in the html. When button clicked, contents of external file sampletextcontent.txt is displayed within said div)
jquery IS being used, version 2.0.3 jquery.min.js
So I am trying (and this is where I am failing) is to convert the above to become:
$("document").ready(function() {
$("#input_1_1").onblur(doSend);
$("#input_1_2").onblur(doSend);
$("#input_1_3").onblur(doSend);
$("#input_1_4").onblur(doSend);
$("#input_1_5").onblur(doSend); // etc for as many fields there are
})
function doSend() {
// Do some ajax stuff to send the entire value of all form fields in here
}
But it does not seem to like the concept of using the replacement of the ".click" to ".onblur" here. Why is this? Isn't onblur a valid JS function/item?
Sorry I'm not a JS guru, I have great problems understanding JS.
C
Edit - sorry I was not clear about the code I am trying to get working. There is no button in the version I want to work, it's just wanting to trigger by when a user clicks/tabs away from each input field. Sorry about not making that clear before.

For dynamic jQuery event binding, I would try switching out the .click and .blur functions with the .on function.
As an example, I would try the following:
$('body').on('click', '#getcontent', function(){
DoSomething();
});
and
$('body').on('blur', '#input_1_1', function(){
DoSomething();
});
The documentation for the on function can be found http://api.jquery.com/on/.
Here is another Stack Overflow article that also explains this: Event binding on dynamically created elements?.

Thanks to the comments and answer attempts. However the answer that I'm using, that actually does answer the specific question is the following. Simply change:
$("document").ready(function() {
$("#input_1_1").onblur(doSend);
$("#input_1_2").onblur(doSend);
$("#input_1_3").onblur(doSend);
$("#input_1_4").onblur(doSend);
$("#input_1_5").onblur(doSend); // etc for as many fields there are
})
To become:
$("document").ready(function() {
$("#input_1_1").blur(doSend);
$("#input_1_2").blur(doSend);
$("#input_1_3").blur(doSend);
$("#input_1_4").blur(doSend);
$("#input_1_5").blur(doSend); // etc for as many fields there are
})
And it works. This retains the ability to call different functions per field if I so wish, and is very straightforward for a JS novice like me to work with.
A better cleaner solution may be implemented later, but for now this will do and directly answers the original question.

Connecting a dojo Autocompleter to a javascript function

I am trying to call a java script function when the selected value in a Dojo auto-completer is changed, but I am unable to do so.
Firstly because the standard onchange attribute does not work here, as this is not a standard HTML component.
Secondly I found this documentation ( http://dojotoolkit.org/reference-guide/quickstart/events.html#connecting-to-a-dom-event ) and it is supposed to solve my problem. But somehow I am still not able to connect to a javascript function.
Here is the sample page through which I am trying to test this out.
The JSP:
<s:form id="form">
<sd:autocompleter id="try" list="sampleList"/>
</s:form>
The JS File:
dojo.connect(dojo.byId("try"),"onchange", tryAlert);
function tryAlert(){
alert('successful');
}
I don't know what I have interpreted wrong from the documentation.
Please advise.
Thanks!!

Here is what I ended up doing. For those still stuck in a similar situation, this will be helpful.
In the jsp File do this:
<s:form id="form">
<s:hidden id="chngd"/>
<sd:autocompleter id="try" list="sampleList" valueNotifyTopics="topic"/>
///////////
//Here you can put more autocompleters if you need them , Like I needed them
///////////
</s:form>
In the js file do this:
dojo.event.topic.subscribe("topic", function(){
dojo.byId('chngd').value='try';// I have set the value of the hidden field to desired value here....
//whatever more you want to do....
});
//////////
//Here there would be a subscription (similar to above) for each autocompleter you have put in your jsp.
//////////
So what will happen here is that, whenever an autocompleter is changed it will notify or publish a topic for listeners to listen. Now the subscribe function in java script will listen to its respective 'topic' and when that topic is published, the subscribe will execute the javascript function inside it.
This way whenever an autocompleter is changed a respective javascript function is called, thus we have a -- onchange="javascript function" -- kind of effect.
If you still face trouble, ask for help :).

Ok I guess the struts component for "autocompleter" is dojo's dijit.form.FilteringSelect.
You will find its documentation at http://dojotoolkit.org/api. Once there, open the tree and follow the path dijit/form/FilteringSelect, then deploy the "Event summary" header.
You will find the list of extension points (say events...) the widget accepts. The correct one for you is called "onChange" (mind the capital C).
Also, dojo widgets can be found by id through dijit.byId("yourId") - dojo.byId is for regular dom nodes.
So, for using the onChange extension point, you should do :
<s:form id="form">
<sd:autocompleter id="try" list="sampleList">
<script type="dojo/method" event="onChange" args="newValue">
alert('successful');
</script>
</s:form>
or... if you prefer the javascript way :
dojo.ready(function(){
dijit.byId("try").onChange = function(newValue) {
alert("Changed to new value", newValue);
}
}

User control with a client side API

Maybe I've picked a totally inappropriate/bad example.
What I have is a user control that contains a bunch of dynamically created Telerik RadGrids.
My user control is added to a couple of Telerik RadPageViews that are part of a RadMultiPage that is used alongside a RadTabStrip.
What I need to do is call a Javascript function in my usercontrol to update it's display whenever it's parent RadPageView is selected.
So basically I have the following Javascript code:
function OnClientTabSelected(sender, args)
{
// Get the MyControl that is on this tab
var myControl = $find("whatever");
// Call a method that updates the display
myControl.doSomething();
}
Thanks,
David

You can add a wrapper div in your User Control and then extend that div using jQuery to add your desired methods and properties. The trick is to set the div's id='<%=this.ID%>' - that way the div has the same ID as the User Control (which is fine because the User Control doesn't actually render anything - only its contents).
Then back on your containing page, you can just reference your UserControl's ID using $get('whatever') - and you'll actually select your extended div.. which will have all your methods and properties on it.
The nice thing about this approach is that all of your methods and properties and neatly scoped and nothing is in the global namespace.
I have a full demo solution and details here if you want more info:
http://programmerramblings.blogspot.com/2011/07/clientside-api-for-aspnet-user-controls.html

Just make a call to javascript method in input button if you are sure about the name of that function.
<input type="button" value="test" onclick="doSomething()" />
If you place any javascript code in the control that will be spit on the page and it will be available for calling provided both of them are in the same form.
for example your code will look like this if you look into the source of that page.
<script type="text/javascript">
function doSomething()
{
alert(new Date());
}
</script>
<div>
<span id="MyControl1_Label1">Dummy label</span>
</div>
<hr />
<input type="button" value="test" onclick="doSomething()" />
Edit: This is not a good way to access these methods in my opinion. When you are putting some javascript code inside a control then it should be used in that control only (There is no rule as such, its just a design suggestion). If you are trying to access javascript code of a control from outside that control then you need to revisit your design.
If you can give us more details on why you want to access that method, may be we can suggest some better way to do that.
Update: (As you have modified your question): Bit tricky to answer this as I dont have hands on experience with Rad controls. I guess there should be some feature which will help you to update the controls in that page without using javascript, may be have a look at clientside-API provided for Rad.
May be somebody who knows about RAD controls will help you.

You should make the control method public
public void doSomething
and call this from the page
myControl1.doSomething();

How to store arbitrary data for some HTML tags

I'm making a page which has some interaction provided by javascript. Just as an example: links which send an AJAX request to get the content of articles and then display that data in a div. Obviously in this example, I need each link to store an extra bit of information: the id of the article. The way I've been handling it in case was to put that information in the href link this:
<a class="article" href="#5">
I then use jQuery to find the a.article elements and attach the appropriate event handler. (don't get too hung up on the usability or semantics here, it's just an example)
Anyway, this method works, but it smells a bit, and isn't extensible at all (what happens if the click function has more than one parameter? what if some of those parameters are optional?)
The immediately obvious answer was to use attributes on the element. I mean, that's what they're for, right? (Kind of).
<a articleid="5" href="link/for/non-js-users.html">
In my recent question I asked if this method was valid, and it turns out that short of defining my own DTD (I don't), then no, it's not valid or reliable. A common response was to put the data into the class attribute (though that might have been because of my poorly-chosen example), but to me, this smells even more. Yes it's technically valid, but it's not a great solution.
Another method I'd used in the past was to actually generate some JS and insert it into the page in a <script> tag, creating a struct which would associate with the object.
var myData = {
link0 : {
articleId : 5,
target : '#showMessage'
// etc...
},
link1 : {
articleId : 13
}
};
<a href="..." id="link0">
But this can be a real pain in butt to maintain and is generally just very messy.
So, to get to the question, how do you store arbitrary pieces of information for HTML tags?

Which version of HTML are you using?
In HTML 5, it is totally valid to have custom attributes prefixed with data-, e.g.
<div data-internalid="1337"></div>
In XHTML, this is not really valid. If you are in XHTML 1.1 mode, the browser will probably complain about it, but in 1.0 mode, most browsers will just silently ignore it.
If I were you, I would follow the script based approach. You could make it automatically generated on server side so that it's not a pain in the back to maintain.

If you are using jQuery already then you should leverage the "data" method which is the recommended method for storing arbitrary data on a dom element with jQuery.
To store something:
$('#myElId').data('nameYourData', { foo: 'bar' });
To retrieve data:
var myData = $('#myElId').data('nameYourData');
That is all that there is to it but take a look at the jQuery documentation for more info/examples.

Just another way, I personally wouldn't use this but it works (assure your JSON is valid because eval() is dangerous).
<a class="article" href="link/for/non-js-users.html">
<span style="display: none;">{"id": 1, "title":"Something"}</span>
Text of Link
</a>
// javascript
var article = document.getElementsByClassName("article")[0];
var data = eval(article.childNodes[0].innerHTML);

Arbitrary attributes are not valid, but are perfectly reliable in modern browsers. If you are setting the properties via javascript, than you don't have to worry about validation as well.
An alternative is to set attributes in javascript. jQuery has a nice utility method just for that purpose, or you can roll your own.

A hack that's going to work with pretty much every possible browser is to use open classes like this: <a class='data\_articleid\_5' href="link/for/non-js-users.html>;
This is not all that elegant to the purists, but it's universally supported, standard-compliant, and very easy to manipulate. It really seems like the best possible method. If you serialize, modify, copy your tags, or do pretty much anything else, data will stay attached, copied etc.
The only problem is that you cannot store non-serializable objects that way, and there might be limits if you put something really huge there.
A second way is to use fake attributes like: <a articleid='5' href="link/for/non-js-users.html">
This is more elegant, but breaks standard, and I'm not 100% sure about support. Many browsers support it fully, I think IE6 supports JS access for it but not CSS selectors (which doesn't really matter here), maybe some browsers will be completely confused, you need to check it.
Doing funny things like serializing and deserializing would be even more dangerous.
Using ids to pure JS hash mostly works, except when you try to copy your tags. If you have tag <a href="..." id="link0">, copy it via standard JS methods, and then try to modify data attached to just one copy, the other copy will be modified.
It's not a problem if you don't copy tags, or use read only data. If you copy tags and they're modified you'll need to handle that manually.

Using jquery,
to store: $('#element_id').data('extra_tag', 'extra_info');
to retrieve: $('#element_id').data('extra_tag');

I know that you're currently using jQuery, but what if you defined the onclick handler inline. Then you could do:
<a href='/link/for/non-js-users.htm' onclick='loadContent(5);return false;'>
Article 5</a>

You could use hidden input tags. I get no validation errors at w3.org with this:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang='en' xml:lang='en' xmlns='http://www.w3.org/1999/xhtml'>
<head>
<meta content="text/html;charset=UTF-8" http-equiv="content-type" />
<title>Hello</title>
</head>
<body>
<div>
<a class="article" href="link/for/non-js-users.html">
<input style="display: none" name="articleid" type="hidden" value="5" />
</a>
</div>
</body>
</html>
With jQuery you'd get the article ID with something like (not tested):
$('.article input[name=articleid]').val();
But I'd recommend HTML5 if that is an option.

Why not make use of the meaningful data already there, instead of adding arbitrary data?
i.e. use <a href="/articles/5/page-title" class="article-link">, and then you can programmatically get all article links on the page (via the classname) and the article ID (matching the regex /articles\/(\d+)/ against this.href).

As a jQuery user I would use the Metadata plugin. The HTML looks clean, it validates, and you can embed anything that can be described using JSON notation.

This is good advice. Thanks to #Prestaul
If you are using jQuery already then you should leverage the "data"
method which is the recommended method for storing arbitrary data on a
dom element with jQuery.
Very true, but what if you want to store arbitrary data in plain-old HTML? Here's yet another alternative...
<input type="hidden" name="whatever" value="foobar"/>
Put your data in the name and value attributes of a hidden input element. This might be useful if the server is generating HTML (i.e. a PHP script or whatever), and your JavaScript code is going to use this information later.
Admittedly, not the cleanest, but it's an alternative. It's compatible with all
browsers and is valid XHTML. You should NOT use custom attributes, nor should you really use attributes with the 'data-' prefix, as it might not work on all browsers. And, in addition, your document will not pass W3C validation.

As long as you're actual work is done serverside, why would you need custom information in the html tags in the output anyway? all you need to know back on the server is an index into whatever kind of list of structures with your custom info. I think you're looking to store the information in the wrong place.
I will recognize, however unfortunate, that in lots of cases the right solution isn't the right solution. In which case I would strongly suggest generating some javascript to hold the extra information.
Many years later:
This question was posted roughly three years before data-... attributes became a valid option with the advent of html 5 so the truth has shifted and the original answer I gave is no longer relevant. Now I'd suggest to use data attributes instead.
<a data-articleId="5" href="link/for/non-js-users.html">
<script>
let anchors = document.getElementsByTagName('a');
for (let anchor of anchors) {
let articleId = anchor.dataset.articleId;
}
</script>

I advocate use of the "rel" attribute. The XHTML validates, the attribute itself is rarely used, and the data is efficiently retrieved.

So there should be four choices to do so:
Put the data in the id attribute.
Put the data in the arbitrary attribute
Put the data in class attribute
Put your data in another tag
http://www.shanison.com/?p=321

You could use the data- prefix of your own made attribute of a random element (<span data-randomname="Data goes here..."></span>), but this is only valid in HTML5. Thus browsers may complain about validity.
You could also use a <span style="display: none;">Data goes here...</span> tag. But this way you can not use the attribute functions, and if css and js is turned off, this is not really a neat solution either.
But what I personally prefer is the following:
<input type="hidden" title="Your key..." value="Your value..." />
The input will in all cases be hidden, the attributes are completely valid, and it will not get sent if it is within a <form> tag, since it has not got any name, right?
Above all, the attributes are really easy to remember and the code looks nice and easy to understand. You could even put an ID-attribute in it, so you can easily access it with JavaScript as well, and access the key-value pair with input.title; input.value.

One possibility might be:
Create a new div to hold all the extended/arbitrary data
Do something to ensure that this div is invisible (e.g. CSS plus a class attribute of the div)
Put the extended/arbitrary data within [X]HTML tags (e.g. as text within cells of a table, or anything else you might like) within this invisible div

Another approach can be to store a key:value pair as a simple class using the following syntax :
<div id="my_div" class="foo:'bar'">...</div>
This is valid and can easily be retrieved with jQuery selectors or a custom made function.

In html, we can store custom attributes with the prefix 'data-' before the attribute name like
<p data-animal='dog'>This animal is a dog.</p>.
Check documentation
We can use this property to dynamically set and get attributes using jQuery like:
If we have a p tag like
<p id='animal'>This animal is a dog.</p>
Then to create an attribute called 'breed' for the above tag, we can write:
$('#animal').attr('data-breed', 'pug');
To retrieve the data anytime, we can write:
var breedtype = $('#animal').data('breed');

At my previous employer, we used custom HTML tags all the time to hold info about the form elements. The catch: We knew that the user was forced to use IE.
It didn't work well for FireFox at the time. I don't know if FireFox has changed this or not, but be aware that adding your own attributes to HTML elements may or may-not be supported by your reader's browser.
If you can control which browser your reader is using (i.e. an internal web applet for a corporation), then by all means, try it. What can it hurt, right?

This is how I do you ajax pages... its a pretty easy method...
function ajax_urls() {
var objApps= ['ads','user'];
$("a.ajx").each(function(){
var url = $(this).attr('href');
for ( var i=0;i< objApps.length;i++ ) {
if (url.indexOf("/"+objApps[i]+"/")>-1) {
$(this).attr("href",url.replace("/"+objApps[i]+"/","/"+objApps[i]+"/#p="));
}
}
});
}
How this works is it basically looks at all URLs that have the class 'ajx' and it replaces a keyword and adds the # sign... so if js is turned off then the urls would act as they normally do... all "apps" (each section of the site) has its own keyword... so all i need to do is add to the js array above to add more pages...
So for example my current settings are set to:
var objApps= ['ads','user'];
So if i have a url such as:
www.domain.com/ads/3923/bla/dada/bla
the js script would replace the /ads/ part so my URL would end up being
www.domain.com/ads/#p=3923/bla/dada/bla
Then I use jquery bbq plugin to load the page accordingly...
http://benalman.com/projects/jquery-bbq-plugin/

I have found the metadata plugin to be an excellent solution to the problem of storing arbitrary data with the html tag in a way that makes it easy to retrieve and use with jQuery.
Important: The actual file you include is is only 5 kb and not 37 kb (which is the size of the complete download package)
Here is an example of it being used to store values I use when generating a google analytics tracking event (note: data.label and data.value happen to be optional params)
$(function () {
$.each($(".ga-event"), function (index, value) {
$(value).click(function () {
var data = $(value).metadata();
if (data.label && data.value) {
_gaq.push(['_trackEvent', data.category, data.action, data.label, data.value]);
} else if (data.label) {
_gaq.push(['_trackEvent', data.category, data.action, data.label]);
} else {
_gaq.push(['_trackEvent', data.category, data.action]);
}
});
});
});
<input class="ga-event {category:'button', action:'click', label:'test', value:99}" type="button" value="Test"/>

My answer might not apply to your case. I needed to store a 2D table in HTML, and i needed to do with fewest possible keystrokes. Here's my data in HTML:
<span hidden id="my-data">
IMG,,LINK,,CAPTION
mypic.jpg,,khangssite.com,,Khang Le
funnypic.jpg,,samssite.com,,Smith, Sam
sadpic.png,,joyssite.com,,Joy Jones
sue.jpg,,suessite.com,,Sue Sneed
dog.jpg,,dogssite.com,,Brown Dog
cat.jpg,,catssite.com,,Black Cat
</span>
Explanation
It's hidden using hidden attribute. No CSS needed.
This is processed by Javascript. I use two split statements, first on newline, then on double-comma delimiter. That puts the whole thing into a 2D array.
I wanted to minimize typing. I didn't want to redundantly retype the fieldnames on every row (json/jso style), so i just put the fieldnames on the first row. That a visual key for the programmer, and also used by Javascript to know the fieldnames. I eliminated all braces, brackets, equals, parens, etc. End-of-line is record delimiter.
I use double-commas as delimiters. I figured no one would normally use double-commas for anything, and they're easy to type. Beware, programmer must enter a space for any empty cells, to prevent unintended double-commas. The programmer can easily use a different delimiter if they prefer, as long as they update the Javascript. You can use single-commas if you're sure there will be no embedded commas within a cell.
It's a span to ensure it takes up no room on the page.
Here's the Javascript:
// pull 2D text-data into array
let sRawData = document.querySelector("#my-data").innerHTML.trim();
// get headers from first row of data and load to array. Trim and split.
const headersEnd = sRawData.indexOf("\n");
const headers = sRawData.slice(0, headersEnd).trim().split(",,");
// load remaining rows to array. Trim and split.
const aRows = sRawData.slice(headersEnd).trim().split("\n");
// trim and split columns
const data = aRows.map((element) => {
return element.trim().split(",,");
});
Explanation:
JS uses lots of trims to get rid of any extra whitespace.