Podcast
Questions and Answers
What is the primary purpose of event delegation in event handling?
What is the primary purpose of event delegation in event handling?
- To improve the performance of the application
- To handle events triggered by a single element
- To reduce the number of event listeners (correct)
- To make the code more modular and reusable
What happens when an event is triggered on a DOM element?
What happens when an event is triggered on a DOM element?
- The event is immediately handled by the element itself
- The event is ignored and not propagated
- The event is captured by the nearest ancestor element
- The event bubbles up the DOM tree and triggers the event handler (correct)
What is the benefit of updating DOM elements dynamically?
What is the benefit of updating DOM elements dynamically?
- It improves the user experience by providing instant feedback (correct)
- It makes the application more vulnerable to security threats
- It increases the loading time of the application
- It reduces the complexity of the code
What is the relationship between event handling and application state?
What is the relationship between event handling and application state?
What is the advantage of using event handling in a web application?
What is the advantage of using event handling in a web application?
The document.querySelectorAll method returns a single element that matches the specified CSS selector.
The document.querySelectorAll method returns a single element that matches the specified CSS selector.
The parentNode.appendChild method inserts a new node before the reference node.
The parentNode.appendChild method inserts a new node before the reference node.
The element.getAttribute method sets an attribute on an element.
The element.getAttribute method sets an attribute on an element.
The element.removeEventListener method adds an event listener to an element.
The element.removeEventListener method adds an event listener to an element.
The document.createElement method creates a new element with the specified ID.
The document.createElement method creates a new element with the specified ID.
The element.getElementsByTagName method selects all elements with the specified class name.
The element.getElementsByTagName method selects all elements with the specified class name.
The element.addEventListener method only works for mouse events.
The element.addEventListener method only works for mouse events.
The parentNode.removeChild method appends a child node to the parent node.
The parentNode.removeChild method appends a child node to the parent node.
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Study Notes
Element Selection
document.getElementById(id)is used to select an element with a specified IDdocument.querySelector(selector)selects the first element that matches a specified CSS selectordocument.querySelectorAll(selector)selects all elements that match a specified CSS selectorelement.getElementsByClassName(className)selects all elements with a specified class nameelement.getElementsByTagName(tagName)selects all elements with a specified tag name
DOM Manipulation
Creating Elements
document.createElement(tagName)creates a new element with a specified tag name
Appending and Inserting Elements
parentNode.appendChild(childNode)appends a child node to a parent nodeparentNode.insertBefore(newNode, referenceNode)inserts a new node before a reference node
Removing Elements
parentNode.removeChild(childNode)removes a child node from a parent node
Modifying Element Attributes and Properties
element.setAttribute(attributeName, attributeValue)sets an attribute on an elementelement.getAttribute(attributeName)gets the value of an attribute on an elementelement.property = valuesets a property on an element (e.g.element.src = 'image.jpg')
Event Listeners
Types of Events
- Mouse events (e.g.
click,mouseover,mouseout) - Keyboard events (e.g.
keydown,keyup) - Form events (e.g.
submit,change) - Window events (e.g.
load,resize)
Adding Event Listeners
element.addEventListener(eventType, listener)adds an event listener to an elementelement.removeEventListener(eventType, listener)removes an event listener from an element
Event Listener Functions
function(event) {...}is a function that is called when an event occursevent.targetis the element that triggered the eventevent.preventDefault()prevents the default action of the event from occurring
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