The 'id' and 'class' attributes are used to select and style HTML elements in a web page. They are both used to give an element a unique identifier so that it can be manipulated with CSS styles or JavaScript code. However, there are some differences between the two:

1. 'id' attribute:

• Each 'id' value must be unique within a web page.
• It is used to select a single specific element.
• Syntax: <element id="id_value">

1. 'class' attribute:

• A single element can have multiple classes.
• Multiple elements can share the same class.
• Syntax: <element class="class_value">

So, you can think of 'id' as a unique identifier for a specific element, while 'class' is a way to group elements that share similar styles or behavior.

You can get the ID of an element in jQuery using the hover or click event by using the this keyword. The this keyword refers to the element that the event is being bound to.

For example, to get the ID of a clicked element with the click event:

javascriptCopy code$(document).on("click", "element_selector", function(){ 
  var id = $(this).attr("id"); 
  console.log(id); 
}); 

Similarly, to get the ID of an element being hovered over with the hover event:

javascriptCopy code$("element_selector").hover(function(){ 
  var id = $(this).attr("id"); 
  console.log(id); 
}); 

Note that element_selector can be a class, id, or any other selector that you would use to target elements in jQuery.

Using jQuery you can do this in multiple ways.

the simplest of ways would be the following

var indexToFind = 1;  
var divClass = jQuery('div[index="'+indexToFind+'"]').eq(0).attr('class');   

This is an attribute selector. The scope of this one is pretty wide, meaning it’s expensive performance wise to run. If you only do it on an action, or on a small page, it’s not too bad, but if this is running in a logic loop, or on a large page, it can be quite a performance hit.

If you do not have any other way of finding the div, you should look into narrowing the scope of the selector.

If you know the parent (or one of the parents) of the div

you could do either one of these:

if you know the parent

var indexToFind = 1; 
var divClass = jQuery('#IdOfParent').children('div[index="'+indexToFind+'"]').eq(0).attr('class');  

This is a simple selector first, and then a children selector. This means we only look at the immediate children of an element

if you know a parent but not the specific parent.

var indexToFind = 1; 
var divClass = jQuery('div[index="'+indexToFind+'"]', '#idOfAParent').eq(0).attr('class');  

this is a context selector.

It means we look at the elements that are nested inside the element(s) of the second selector. (‘#idOfAParent’)

You can chage the #idOfParent & #idOfAParent to any selector, in order to narrow down the scope, but you should try to stick with either ID or class selector.

I would also recommend you read up on selectors and attribute selectors

Below you will find a link to the jQuery documentation.

jQuery API Documentation (Selectors in general)

jQuery API Documentation (Attribute selectors)

Hope this helps :-)

Let's start with assumptions. I'll assume that you're talking exclusively about HTML manipulation, don't have jQuery available, that you already have a reference to the parent node in the variable parent, and that you have the "specific class name", which represents exactly one class, stored in the variable className. Moreover, I’ll use only ES5 syntax.

In that case, it's as simple as using the getElementsByClassName and removeChild methods together on the parent node:

var child; 
for (child in parent.getElementsByClassName(className)) { 
    if (parent.hasOwnProperty(child)) { 
        parent.removeChild(child); 
    } 
} 

If you do have jQuery available, then it's even simpler:

$(parent).children("." + className).remove(); 

jQuery selectors allow you to select and manipulate HTML element(s).

jQuery selectors are used to "find" (or select) HTML elements based on their name, id, classes, types, attributes, values of attributes and much more.

The #id Selector

The jQuery #id selector uses the id attribute of an HTML tag to find the specific element.

An id should be unique within a page, so you should use the #id selector when you want to find a single, unique element.

To find an element with a specific id, write a hash character, followed by the id of the HTML element:

$("#test") 

Example

When a user clicks on a button, the element with id="test" will be hidden:

Sample code

$(document).ready(function(){ 
 $("button").click(function(){ 
  $("#test").hide(); 
  }); 
}); 

The .class Selector

The jQuery .class selector finds elements with a specific class.

To find elements with a specific class, write a period character, followed by the name of the class:

$(".test") 

Example

When a user clicks on a button, the elements with class="test" will be hidden:

Sample code

$(document).ready(function(){ 
  $("button").click(function(){ 
  $(".test").hide(); 
 }); 
}); 

You may also get elements from more than one class by delimiting class names with comma, e.g. $(".class1, .class2").

If you are look for elements within a particular element,
e.g.

<div id="div1"> 
    <div class="class1">...</div> 
    <div class="class1">...</div> 
    <div class="class2">...</div> 
    <p>...</p> 
    <p>...</p> 
</div> 
<div>...</div> 

you might want to initialize "div1" to a variable and then find only elements within it using .find(...) instead of using $(...), which will search the entire DOM every time it is invoked.
Example:

var div1 = $("#div1"); 
var p_tags_in_div1 = div1.find("p"); 
var class2_in_div1 = div1.find(".class1"); 

through jQuery you can use $(this) to access the clicked element like in the following code:-

When you say “by ID” and “like jQuery”, I assume you mean selecting an element using it’s ID attribute, and then using one of the class methods to add or remove a class name? Something like this:

$(‘#my-element’).addClass(‘new-class’); 

The answer is that you don’t do this in Angular. Not in AngularJS, or in modern Angular2+.

Selecting elements from the DOM is expensive, and it’s easy to do it badly in jQuery. Angular takes a different approach. Instead you use a directive to add, remove, or change class names. In your mark-up, you add the directive to the element:

<span ngClass=“{ hasClass: ‘new-class’ }”>I am a span</span> 

The ngClass directive takes an object; the key of the object is used to determine whether the element has the class or not, and the value is the new class name to add to the element if the key is true. You can have as many key:value pairs as you like, I just used 1 to keep it simple.

Now in your component class, you can have a simple property of the class called hasClass and whenever that property is true, the element will have the class, and whenever the property is false, the element will not have the class.

You don’t need to worry about selecting the element from the DOM, Angular takes care of that in an optimal way. You just need to manage a simple Boolean property in your class.

You can get the value of an input element in jQuery using the val method. Here's an example:

<input type="text" id="input_field"> 
 
<script> 
  $(document).ready(function() { 
    var inputValue = $("#input_field").val(); 
    console.log(inputValue); 
  }); 
</script> 

In this example, the input element has an id attribute of input_field, which is used to select the element using the jQuery selector $("#input_field"). The val method is then used to get the value of the input element, which is stored in the inputValue variable. You can also use the val method to set the value of an input element by passing a value as an argument:

$("#input_field").val("Hello, World!"); 

This code sets the value of the input element to "Hello, World!".