jQuery Selectors and the filter() Method: Mastering DOM Element Selection
This tutorial provides a comprehensive guide to jQuery selectors, covering various selector types and the powerful filter() method for refining element selections. Learn how to efficiently target specific HTML elements and manipulate the DOM using jQuery's versatile selection capabilities.
jQuery Interview Questions and Answers
jQuery Selectors
Question 24: jQuery Selectors
jQuery selectors find HTML elements. Types include:
- Element Selector:
$("p")selects all paragraph elements. - Id Selector:
$("#myId")selects the element with id "myId". - Class Selector:
$(".myClass")selects all elements with class "myClass". - Universal Selector:
$("*")selects all elements. - Multiple Selectors:
$("p, div, a")selects paragraphs, divs, and anchors. - Attribute Selectors: Select elements based on attributes (e.g.,
$("a[href]")).
jQuery filter() Method
Question 25: jQuery filter() Method
The filter() method allows selecting elements from a jQuery object that match a specified criteria. It narrows down your selection from an existing set of elements.
jQuery Selector Types
Question 26: Types of jQuery Selectors
jQuery supports:
- CSS selectors: Most common; use CSS syntax.
- Custom selectors: For creating custom selectors.
- XPath selectors: Used to select XML elements.
ID vs. Class Selectors
Question 27: ID vs. Class Selectors
An ID selector selects a *single* element by its ID; a class selector selects *multiple* elements with a common class name. IDs should be unique on a page.
serialize() Method
Question 28: serialize() Method
The serialize() method creates a URL-encoded string of form element values. This is handy for submitting form data via AJAX.
Example
$(document).ready(function() {
$("button").click(function() {
$("div").text($("form").serialize());
});
});
(HTML form would be needed here to show a complete working example.)
val() Method
Question 29: val() Method
The val() method gets or sets the value of form elements.
Example: Getting the value
let value = $("#myInput").val();
(HTML input element would be needed here for a complete example.)
Adding and Removing CSS Classes
Question 30: Adding and Removing CSS Classes
Use addClass() to add and removeClass() to remove CSS classes.
addClass() Example
$(document).ready(function(){
$("#btn").click(function(){
$("#para").addClass("change");
});
});
Output
Paragraph text turns blue on button click.
removeClass() Example
$(document).ready(function(){
$("#btn").click(function(){
$("p").removeClass("change");
});
});
Output
Paragraph text color reverts to default on button click.
Selecting Links Within Paragraphs
Question 31: Selecting Links Inside Paragraphs
jQuery Code
$(document).ready(function() {
$("p a").attr("href", "https://tutorialsarena.com/");
});
Output
All links inside paragraphs will point to tutorialsarena.com
`attr()` vs. `prop()`
Question 32: `attr()` vs. `prop()`
Differences:
attr()gets or sets attribute values (HTML attributes).prop()gets or sets property values (JavaScript properties).
CDNs (Content Delivery Networks)
Question 33: Types of CDNs
Common CDNs for jQuery:
- Google Hosted Libraries
- Microsoft AJAX CDN
animate() Method
Question 34: animate() Method
The animate() method applies custom animations to elements. You specify CSS properties and duration. Easing functions and callbacks can also be used.
Example
$("#myDiv").animate({left: '250px'}, 1000); //Moves the div 250px to the right over 1 second
Disabling jQuery Animations
Question 35: Disabling jQuery Animations
Set jQuery.fx.off = true; to disable animations.
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