Develop Reference

How do you assign new atrributes to elements in reactjs

I was going through a tutorial and came across these lines of code but I dont understand the meaning of the 'data-behavior' and 'data-animation' attributes.
<div className='row animated fadeInUp' data-animation='fadeInUp-fadeOutDown'>
....
</div>

These atributes allow you to pass any kind of data in your html tag. They are "homemade" attributes that you can use and access like any other.
You can have some explanation here.
Common usages are passing along a url that you will use in javascript in a data-url attribute, or any kind of values, really.

The data- attribute is given to HTML elements when we want to provide extra data to them, without breaking the W3C convention and default attributes.
See https://developer.mozilla.org/en-US/docs/Learn/HTML/Howto/Use_data_attributes
Whilst the data-* attributes are really helpful in conventional web development, i.e. developing apps raw and without JavaScript, there are several workarounds in React.JS that will not prove to be a headache.
Please provide extra information

Javascript/HTML: Using id vs. class when naming

I am starting to learn some Javascript using Meteor and am looking at their examples.
One bug that tripped me up for a bit happened when I was adding a text-field for input with a button next to it; users would type in a name they wanted to add to a list and then click the button to actually add it.
My question is: why does it seem to be the case that in the html, the text field has to be named with id="..." while the button has to be named with class="..."?
For additional reference, in my javascript file, I am using textfieldname.value and 'click input.buttonname'. Does the id vs. class requirement stem from how I'm using them?

The "id" attribute is used to supply a globally-unique identifier for an element. The "class" attribute is used to categorize or typify an element according to its meaning, its intended use, its relationship to other elements, or whatever else your application requires.
Usually it's more flexible to use classes to identify things, because more than one element can be given the same class, and an element can have as many classes as are needed. Any single element may only have one "id", and the values must not be re-used in the same document. There are clear use cases for both attributes in which one or the other is obviously more appropriate, and many other cases where it's less clear and for which either could be used.
This isn't really a JavaScript issue so much as a "web application design" issue. How one labels HTML elements is dictated by the nature of the content (HTML), the needs of the presentation (CSS), and the intended behaviors (JavaScript).

Local id-s for HTML elements

I am developing a kind of HTML+JS control which can be embedded into various web pages. I know nothing about those pages (well, I could, but I don't want to). The control consists of one root element (e.g. DIV) which contains a subtree of child elements. In my script, I need to access the child elements. The question is: how can I mark those child elements to distinguish them?
The straightforward solution is using id-s. The problem here is that the id must be unique in the scope of the entire document, and I know nothing about the document my control will be embedded into. So I can't guarantee the uniqueness of my id-s. If the id-s are not unique, it will work (if used with care), but this does not conform with the standard, so I can meet problems with some new versions of the browsers, for example.
Another solution is to use the "name" attribute. It's not required to be unique -- that's good. But again, the standard allows the presence of "name" attribute only for a restricted set of element types. For example, the "name" attribute is invalid for DIV elements.
I could use, for example, the "class" attribute. It seems to be OK with the standards, but it's not OK with the meaning. "class" should be used for other purposes, and this may be confusing.
Can anybody suggest some other options to implement local id-s for HTLM elements?

You could use the HTML5 data-* attributes so you can give them a custom name with the right meaning:
https://html.spec.whatwg.org/multipage/dom.html#embedding-custom-non-visible-data-with-the-data-*-attributes
Do something like:
<div id="element-id" data-local-id="id-value">
...
</div>
and get the value in JavaScript with:
const el = document.getElementById('element-id');
const { localId } = el.dataset;

If you use a prefix to all of your ID's and or classes such as myWidgetName_98345699- the likelihood of collisions is highly improbable.
<div id="myWidgetName_98345699-container" class="myWidgetName_98345699-container">
jQuery does have selectors that will search for part of an ID, so using common names like container would be smart to stay away from as well. Using a longish alphanumeric mix for the specific part of the ID would be smart also

Typically, including hidden information within the web page required creative approaches. For example:
Storing information within HTML element attributes such as id, class, rel, and title, thus overriding the attributes original intent.
Using <span> or <div> blocks that contain the information, while making such blocks invisible to the user through styling (style="display: none;").
Adding JavaScript code to the web page to define data structures that map to HTML ID elements.
Adding your own attributes to existing HTML elements (breaking the HTML standard itself, and relying on the HTML browser to ignore any syntax errors).
The approaches above are not elegant and are not good coding practice, but the good news is that jQuery has a facility that simplifies associating data to DOM elements in a clean, cross-browser manner.
Use the custom data attributes:
Any attribute that starts with "data-" will be treated as a storage area for private data (private in the sense that the end user can't see it - it doesn't affect layout or presentation.
Defining custom data via html:
<div class="bar" id="baz" data-id="foo">
...
</div>
Associating data-id to specific DOM elements (jQuery):
$('#foo').data('id', 'baz');
Retrieving an element with specific data-id:
var $item = $('*[data-id="baz"]');

xml inside html

What is the issue regarding placing xml elements inside html ? I am trying to easily retrieve javascript event info which returns some html when a div is clicked on. I want to parse that (as I cant send any data object afaik) and its very easy so I'm doing
<div><currency>eur</currency><price>120</price><weight>2kg</weight></div>
and in the js im doing
doTap=function(sent) {
console.log(sent.getElementsByTagName('price')[0].innerHTML);

The issue is that XML is not valid HTML (with respect to the elements). The browser does not know how to render a currency element, and afaik there is no standard way to deal with unknown elements. Some browsers might ignore them completely.
You should be fine with using span elements and giving them a class:
<div>
<span class="currency">eur</span>
<span class="price">120</span><
<span class="weight">2kg</span>
</div>
a elements are not supposed to contain block elements btw.
Then get the element in question by its class.
If you don't want to display the information (currency, price, etc) but only need to store it somewhere, you can use HTML5's data-* attributes:
<a data-currency-"eur" ... ></a>
and access them with getAttribute.

The main practical problem is that IE 8 and older do not deal at all with tags they don’t know when processing HTML documents. To deal with this, you can add code like document.createElement('currency').
There are other issues, too, such as the risk that some future browsers will start recognizing the markup you have invented – and this may cause unpredictable rendering features and functionality. Some more notes: http://www.cs.tut.fi/~jkorpela/pragmatic-html.html8#custom
The safer approach is to use span elements with class. You can also use a elements, since without href, they are still valid but do not create links, making the element effectively just a text-level container. By HTML syntax rules, though, you must not nest a elements (but browsers don’t care, in things like this).
So the safest approach uses e.g. <span class=currency>EUR</span> etc. instead.

javascript name vs ID

As far as I know there are two ways to get the value from a textbox either
document.formName.textboxName.value;
or
document.getElementbyId('textboxId').value;
As I understand using form name would mean I have less code to write, as name can be used for posting data and getting the value (apart from using ajax). As where if I was just posting using a standard form I would use name to post but I cannot use id ?
e.g. in php I would use
$_POST['texboxName'];
If I where to have and ID on the textbox I cannot get the value using php ?
Which is the standard recommened way of doing this, and is using name browser friendly? Links if possible please, thanks.

The ultimate guide in this is the HTML specification.
Things that stand out there:
id is valid for any HTML element, while name only applies to a select few (a, input, textarea and maybe a few others).
An input (and textarea) element requires the name to be set if you want it to be submitted.

The name attribute is used during submitting the form, i.e. to create a name-value pair that will be processed to the server. The id attribute is used to locate and element in the DOM. Usually the name is used only on the form elements
References:
http://www.w3.org/TR/html401/interact/forms.html
http://www.w3schools.com/html/html_forms.asp

I typically use both. As you mentioned, name is useful for using the data via JavaScript and also once it has been submitted. Feel free to use additional characters in the name as needed: I tend to use []s in my names when the input will be used in an array server-side.
The id attribute can be used for accessing the element via JS/the DOM. It is also used by <label>'s for attribute. If you do this with checkboxes, for example, clicking on the label will cause the box to become checked. That's a big plus for usability.

I consider it good practice to have a name and id for each form element. The reason being that if you want to add labels, or styling via sytlesheets (which you should be doing), then it makes sense to have both.
As for accessing it with javascript: the better way would be to go with the element's id, becuase if you change the name of the form everything breaks. This does not happen when you use the id.

I prefer using IDs, as the "function" (i.e.: what you're trying to achieve) of your code isn't tied up with in the semantics. For me, .GetElementById('myid') stands out more, and is more readable that just having "myid" scattered among the code. Plus you can more easily rename elements. That's my 2p worth!