Develop Reference

Accessing properties of a tag within a tag

I have an a tag as follows:
<a href="data1.html" class="list-group-item" data-toggle="collapse">
<i class="glyphicon glyphicon-folder-close"></i>Root Folder
</a>
I have a function that gets called when you click on a tag. It is as follows -
$(document).ready(function() {
$("a").hover(function(event) {
console.log(event.target.href);
});
});
I can access the properties of a tag. Example: If i want to access the href of the a onclick, I can get it by event.target.href.
I want to access the properties of the i tag that is inside the a tag (for instance, class of i tag is "glyphicon glyphicon-folder-close").
How do I achieve that?
Also, what changes do I have to make to the function, such that it is called only if a tags of class = "list-group-item" are clicked?
Thanks in advance.

I want to access the properties of the i tag that is inside the a tag
Inside any jQuery event handler, this refers to the element on which the event was triggered: therefore you can use any selector relative to that element. $(this).children('i') for example will find the contained i given your HTML; if the element might be nested more deeply you'd want .find() instead of .children().
what changes do I have to make to the function, such that it is called only if a tags of class = "list-group-item"
Change the selector you're using to attach the handler - $("a.list-group-item") instead of $("a") to limit it to items having that class.
Note also that if you want this to work on click as you describe, rather than on hover as in your sample code, you'll need to return false from the event handler (so that the regular link navigation doesn't occur).
$(document).ready(function(e) {
$("a.list-group-item").click(function() {
var myChild = $(this).children('i')
console.log(myChild.attr("class")); // for example
return false; // prevent regular navigation from occurring on click
});
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<a href="https://example.com" class="list-group-item">
<i class="glyphicon glyphicon-folder-close"></i> Will fire handler on click
</a>
<br>
<a href="https://example.com">
<i class="glyphicon glyphicon-folder-close"></i> Will navigate normally
</a>

Since you are using jQuery, this will be very easy!
$(document).ready(function() {
$("a.list-group-item").click(function(event) {
$(this).find('i').attr('class');
});
});
To get only certain anchor tags you can use a selector, read more about them here. Then you can use the this object to find children. Use the find method in jQuery. Finally use the attr to retrieve the class.

You can rewrite your function like this:
$(document).ready(function() {
//Only use list-group-item
$("a.list-group-item").hover(function(event) {
var $attrNode = $(this).find("i");
//Now that you have the list group item it is easy to get the attribute
var attributeValue = $attrNode.attr("your-attribute");
//You can also set the attribute
$attrNode.attr("your-attribute", "attribute value");
});
});

Find element in document using HTML DOM

I need to be able to select and modify an element in an HTML document. The usual way to find an element using jQuery is by using a selector that selects by attribute, id, class or element type.
However in my case I have the element's HTML DOM and I want to find the element on my document that matches this DOM.
Important :
I know I can use a class selector or ID selector etc.. but sometimes the HTMLs I get don't have a class or an ID or an attribute to select with, So I need to be able to select from the element's HTML.
For example here is the element I need to find :
<span class='hello' data='na'>Element</span>
I tried to use jQuery's Find() but it does not work, here is the jsfiddle of the trial : https://jsfiddle.net/ndn9jtbj/
Trial :
el = jQuery("<span class='hello' data='na'>Element</span>");
jQuery("body").find(el).html("modified element");
The following code does not make any change on the element that is present in my HTML and that corresponds to the DOM I have supplied.
Is there any way to get the desired result either using native Javascript or jQuery?

You could filter it by outerHTML property if you are sure how browser had parsed it:
var $el = jQuery("body *").filter(function(){
return this.outerHTML === '<span class="hello" data="na">Element</span>';
});
$el.html("modified element");

el = jQuery('<i class="fa fa-camera"></i>');
This does not say "find the element that looks like <i class="fa fa-camera"></i>". It means "create a new i element with the two classes fa and fa-camera. It's the signature for creating new elements on the fly.
jQuery selectors look like CSS, not like HTML. To find the i element with those two classes, you need a selector like i.fa.fa-camera.
Furthermore $("document") looks for an HTML element called document. This does not exist. To select the actual document, you need $(document). You could do this:
$(document).find('i.fa.fa-camera').html("modified html")
or, more simply, you could do this:
$('i.fa.fa-camera').html('modified html');
You indicate in a comment to your question that you need to find an element based on a string of HTML that you receive. This is, to put it mildly, difficult, because, essentially, HTML ceases to exist once a browser has parsed it. It gets turned into a DOM structure. It can't just be a string search.
The best you can do is something like this:
var searchEl = jQuery('<i class="fa fa-camera"></i>');
var tagName = searchEl.prop('tagName');
var classes = [].slice.apply(searchEl.prop('classList'));
$(tagName + "." + classes.join('.')).html('modified html');
Note that this will only use the tag name and class names to find the element. If you also want IDs or something else, you'd need to add that along the same lines.

You should use Javascript getting the elements by something like
document.getElementById...
document.getElementsByClassName...
document.getElementsByTagName...
Javascript is returning the elements with the Id, Class or Tag Name you chose.

You can get en element with document.querySelector('.fa-camera')
with querySelector you can select IDs and Classes

You can simply refer to it by its class names.
$('.fa.fa-camera').html("modified html");
Similar to this answer https://stackoverflow.com/a/1041352/409556
Here is a full example:
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$('.fa.fa-camera').html("modified html");
});
</script>
</head>
<body>
<i class="fa fa-camera"><h1>Some HTML</h1></i>
</body>
</html>`

The one thing that you could use is to check attributes (class and id goes here too in some way) that element have, and the build jQuery selector or DOM querySelector to find the element you need. The hardest part would be to find element based on innerHTML property - "Element" text inside it, for this one you'll probably have to grab all similar element and then search through them.
<span class='hello' data='na'>Element</span>
jQuery('body').find('span.hello[data=\'na\']').html('modified element')
Take notice of 'span' - that's tag selector, '.hello' - class, '[data="na"]' data attribute with name of data.
Jsfiddle link here that extends your example;

How do you grab an element relative to an Element instance with a selector?

I am writing a small library where I am in need of selecting a relative element to the targeted element through querySelector method.
For example:
HTML
<div class="target"></div>
<div class="relative"></div>
<!-- querySelector will select only this .target element -->
<div class="target"></div>
<div class="relative"></div>
<div class="target"></div>
<div class="relative"></div>
JavaScript
var target = document.querySelectorAll('.target')[1];
// Something like this which doesn't work actually
var relativeElement = target.querySelector('this + .relative');
In the above example, I am trying to select the .relative class element relative only to the .target element whose value is stored in target variable. No styles should apply to the other .relative class elements.
PS: the selectors can vary. So, I can't use JavaScript's predefined methods like previousElementSibling or nextElementSibling.
I don't need solution in jQuery or other JavaScript libraries.

Well it should be ideally:
var relativeElement = target.querySelector('.relative');
But this will actually try to select something inside the target element.
therefore this would only work if your html structure is something like:
<div class="target">
<div class="relative"></div>
</div>
Your best bet would probably in this case be to use nextElementSibling which I understand is difficult for you to use.

You cannot.
If you insist on using the querySelector of the subject element, the answers is there is no way.
The spec and MDN both says clearly that Element.querySelector must return "a descendant of the element on which it is invoked", and the object element you want does not meet this limitation.
You must go up and use other elements, e.g. document.querySelector, if you want to break out.
You can always override Element.prototype.querySelector to do your biddings, including implementing your own CSS engine that select whatever element you want in whatever syntax you want.
I didn't mention this because you will be breaking the assumption of a very important function, easily breaking other libraries and even normal code, or at best slowing them down.

target.querySelector('.relative');
By using querySelector on the target instead of document, you scope the DOM traversal to the target element.
It is not entirely clear from your explanation, but by related i assume you mean descendant?
To get all target elements you can use
document.querySelectorAll('.target')
And then iterate the result

I found a way which will work for my library.
I will replace "this " in the querySelector with a unique custom attribute value. Something like this:
Element.prototype.customQuerySelector = function(selector){
// Adding a custom attribute to refer for selector
this.setAttribute('data-unique-id', '1');
// Replace "this " string with custom attribute's value
// You can also add a unique class name instead of adding custom attribute
selector = selector.replace("this ", '[data-unique-id="1"] ');
// Get the relative element
var relativeElement = document.querySelector(selector);
// After getting the relative element, the added custom attribute is useless
// So, remove it
this.removeAttribute('data-unique-id');
// return the fetched element
return relativeElement;
}
var element = document.querySelectorAll('.target')[1];
var targetElement = element.customQuerySelector('this + .relative');
// Now, do anything with the fetched relative element
targetElement.style.color = "red";
Working Fiddle

Get aria-expanded value

I didn't find a way to get aria-expanded value from DOM.
<a class="accordion-toggle collapsed" href="#collapse-One" data-parent="#accordion-1" data-toggle="collapse" aria-expanded="false">
<i class="fa fa-search-plus"></i>
test
</a>
I want to test if it's true then I can change <i> class to fa-search-minus. I tried this but I always get an undefined value:
console.log($(this).find('a.aria-expanded').val());

I wanted to add in a second pure javascript way to get the aria-expanded attribute
document.getElementById('test').getAttribute('aria-expanded')
The above will get the element by id after that you can get any attribute by name.

aria-expanded is an attribute on the element, not a class, so the selector is incorrect. Secondly, you should use the attr() function to get the value of that attribute. val() is intended to retrieve the value attribute from form related elements, such as input and textarea. Try this:
console.log($(this).find('a[aria-expanded]').attr('aria-expanded'));

You can use JavaScript to achieve this:
document.getElementsByTagName('a')[0].attributes[4].value
Step by step explanation:
Get the wanted element, by using some selector - here I use the
document.getElementsByTagName('a')[0]
but you can use any other selector you like.
Access the attributes array of the element and find the position of the wanted attribute - in this case that will be 4, because aria-expanded is the 5th attribute of the tag.
From there you just get the value, and that should give you "false" (in this case).
The only problem with this method is that it's a bit hard-coded, so if you add some more attributes to the tag, the position in the attributes array for the aria-expanded attribute might change.
UPDATE
Instead of using the index for accessing the Aria Expanded property, you can use the name:
document.getElementsByTagName('a')[0].attributes['aria-expanded'].value
This way you will always get the value for the Area Expanded property, regardless of it's position in the HTML tag.

Update 02/2023:
ariaExpanded property still does not work on Firefox. It will be undefined.
Another way to get aria values is to reference the properties directly:
For your instance, you could do something like this:
let firstAnchorTag = document.getElementsByTagName('a')[0]; // I don't know your situation but I recommend adding an id to this element, or making this an iterable array.
console.log(firstAnchorTag.ariaExpanded); // Should log 'false' for your example.
To get:
let el = document.getElementById('foobar');
console.log(el.ariaExpanded); // Should log the current value of aria-expanded.
To set:
let el = document.getElementById('foobar');
el.ariaExpanded = 'true';
console.log(el.ariaExpanded); // Should log 'true'.
Reference: Element.ariaExpanded MDN

In 2020, I could do:
document.querySelector('[aria-expanded]')?.getAttribute('aria-expanded')
to grab the first value and maybe something like:
Array.from(document.querySelectorAll('[aria-expanded]'))?
.map(el => el.getAttribute('aria-expanded'))
to make an array of all aria-expanded values.

attr() function is used to get value of attribute whereas val() is used to retrieve the value attribute from form the related elements, i.e. textbox,input etc. Also aria-expanded is an attribute not a class so you are using incorrect selector.
So you should use attr() instead of val().
Use this:
console.log($(this).find('a[aria-expanded]').attr('aria-expanded'))

You can get the element by the class name "accordion-toggle" (if you have it just one time), or better add an ID to the element, and then get the attribute.
$('.accordion-toggle').attr('aria-expanded')
Or
$('#id-name').attr('aria-expanded')

jquery hasClass, can it be given the beginning of class name, to get the full class name

I'm trying to do something similar to this question, but it's a bit different, so the solution there isn't working for me.
<span class="a-class another-class test-top-left"></span>
I have an element (this code shows a span but it could be div span or anything). This element has a class beginning with test- (test-top-left, test-top-right etc.) I've triggered a click event on classes starting with test- and saved the clicked object as var object = this;. Simple stuff so far.
What I'm trying to do now is get the full name of that class (test-top-left). I know it starts with test- but what's the full name. The thing is that there are other classes a-class another-class and test-top-left. Can hasClass be used to get the full name of the class? I'd prefer not to use find() or filter() just because there may be additional elements within that also have class="test-"
Edit:
The code I have now is, but it gives me ALL the classes. What I need is the single class beginning with test-.
var object = this;
$(object).attr('class');
So now I for loop through all the classes and test each one separately, which seems like a lot of unnecessary code. I'm hoping jQuery has a clever way to get the exact class that was clicked right away.

Description
You can use jQuerys Attribute Contains Selector, .attr() and .click() method.
Attribute Contains Selector - Selects elements that have the specified attribute with a value containing the a given substring.
.attr() - Get the value of an attribute for the first element in the set of matched elements.
.click() - Bind an event handler to the "click" JavaScript event, or trigger that event on an element.
Sample
html
<span class="anyclass test-hello">Hello World</span>​
jQuery
$("[class*='test']").click(function() {
var object = $(this);
alert(object.attr("class").match(/(test-.*?)(?:\s+|$)/)[1])
;});
Check out the updated jsFiddle
Update
If you dont want to use regex you can do this.
$("[class*='test']").click(function() {
var object = $(this);
alert("test-" + object.attr("class").split("test-")[1].split("-"))
;});
​
More Information
jQuery - Attribute Contains Selector
jQuery - .attr()
jQuery - .click()
jsFiddle Demonstration

This should work for you:
var object = this;
var className = object.className.match(/(test-.*?)(?:\s+|$)/)[1];
Class name is the name of the class you are looking for.

If you don't want to use split or regex, you can try having the class in a separate attribute
<span class="someclass test-something" _rel="test-something">test<span>
or
<span class="someclass" _rel="test-something">test<span>
with the script
$("[_rel*='test-']").click(....
And to retrieve the attribute, use $(this).attr("_rel")