JavaScript and DOM Manipulation Quiz

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Questions and Answers

Which method is used to create a new element in the DOM?

document.addElement()

document.createElement() (correct)

document.insertElement()

document.newElement()

What does the method elem.getAttribute(name) return?

The list of all attributes of the element

True or false indicating if the attribute exists

The default value of the attribute

The value of the specified attribute (correct)

How can you modify the color style of an element using JavaScript?

elem.css('color', 'green');

elem.changeStyle('color', 'green');

elem.style.color = 'green'; (correct)

document.setStyle(elem, 'color', 'green');

Which method is used to remove an attribute from a DOM element?

elem.removeAttribute(name) Signup and view all the answers

What is a potential drawback of using innerHTML to change content?

It can introduce vulnerabilities by allowing rogue code. Signup and view all the answers

What method is used to remove an event handler added with addEventListener?

removeEventListener() Signup and view all the answers

Which of the following is NOT an intrinsic event attribute in HTML?

ondrop Signup and view all the answers

Which statement best describes the role of JavaScript in web development?

JavaScript enables dynamic behavior in web content. Signup and view all the answers

How can you include an external JavaScript file in your HTML?

Which method is used to trigger a function when an HTML document has loaded?

addEventListener('load', function) Signup and view all the answers

What type of JavaScript object does 'null' represent?

Primitive type Signup and view all the answers

Which of the following is not a type of DOM selection method?

selectElement() Signup and view all the answers

What happens when an event handler is executed in JavaScript?

It runs logic in response to a specific event. Signup and view all the answers

Which method is used to add a child node to a parent node in the DOM?

parent.appendChild(childNode) Signup and view all the answers

What is the purpose of the preventDefault() method in event handling?

To prevent the default action of the event from occurring Signup and view all the answers

Which of the following is NOT a phase of DOM event flow?

Event captivation phase Signup and view all the answers

How can you replace one node with another in the DOM?

parentNode.replaceChild(newChild, oldNode) Signup and view all the answers

Which event would you use to detect when a key is pressed down?

keydown Signup and view all the answers

What does the addEventListener() function do?

Binds an event handler to an event for an element Signup and view all the answers

Which property is used to assign an event handler to an element using Node Properties?

onclick Signup and view all the answers

To remove a child node from a parent node, which method is used?

parent.removeChild(childNode) Signup and view all the answers

Study Notes

JavaScript Implementations

JavaScript core comprises three components: ECMAScript, DOM, and BOM
ECMAScript provides the language's core syntax and semantics
DOM (Document Object Model) represents the structure of HTML/XML documents as nodes
BOM (Browser Object Model) provides a programming interface for interacting with the browser environment

Window Object

Properties of the Window object are globally accessible through browser APIs
Properties vary across different browsers due to vendor implementations
innerWidth and innerHeight: size of the viewport (minus borders, toolbars)
outerWidth and outerHeight: size of the entire browser window
resizeTo(x,y) and resizeBy(x,y): method to resize the browser window
window.open(URL, "newFrame"): methods for navigating to a specific URL

Location Object

Provides information about the current document and allows navigation
The location object has properties for describing the current document's URL
Properties include hash, host, hostname, href, pathname, port, protocol, search, username, password, and origin

Navigator Object

Provides information about the user's browser and system environment
Properties include: battery, connection, cookieEnabled, credentials, deviceMemory, doNotTrack, geolocation, getVRDisplays(), getUserMedia(), languages, locks, mediaCapabilities, mediaDevices, maxTouchPoints, online, oscpu, permissions, platform, plugins, registerProtocolHandler, requestMediaKeySystemAccess, and sendBeacon()

Screen Object

Contains properties related to the screen's display dimensions and layout
Properties include: availHeight, availLeft, availTop, availableWidth, colorDepth, height, left, pixelDepth, top, width, and orientation

DOM (Document Object Model)

A structured representation of the HTML structure (representing a web page as a tree)
The root DOM element is the document object
Each element is a node, with attributes (properties)
The DOM can be modified dynamically with JavaScript

Retrieving DOM Nodes

Nested objects/elements accessed via dot notation
Document.images[index]: access a particular image in a document
document.getElementsByTagName(tagname): returns an array of all elements with the specified tag name (including non-matched elements such as paragraphs)
document.getElementById(id): returns the element with the corresponding id attribute
document.getElementsByClassName(classname): Returns an array of all elements with the given class names
document.querySelector/querySelectorAll: Selects the element according to the CSS Selector

Accessing DOM Node Attributes

elem.AttributeName: individual attribute name/value
elem.attributes: attribute collection
elem.hasAttribute(name): checks attribute availability
elem.getAttribute(name): gets attribute value
elem.setAttribute(name, value): sets attribute value
elem.removeAttribute(name): removes attribute
elem.style.CSSAttributeName: access CSS attributes for a node
elem.className: class string name
elem.classList: class list (add/remove/toggle methods)

Accessing DOM Node' Attributes - Examples

getAttribute(“attribute name”) -> retrieves the attribute value
setAttribute(“attribute name”,”new value”): Changes the attribute value

Adding and Removing Elements

document.createElement(tagName): creates a new element
parentNode.appendChild(childNode): adds the node to the end of the parent node
parentNode.insertBefore(InsertedNode,Node2): inserts element before another element
parentNode.replaceChild(newChild, oldChild): replaces a node with another

DOM Events & Event Flow

DOM Event Flow: capturing, target, bubbling
Event handler (event listener): Function called in response to an event
Event handlers often begin with the “on” prefix
Events can be triggered by user interaction or browser actions (e.g., loading a page)

DOM Events Examples

event Object: target, type, preventDefault() for controlling event actions
Keyboard events: key, keyCode, altKey, ctrlKey, shiftKey
Mouse events: pageX, pageY, button, altKey, ctrlKey, shiftKey

DOM Event Handlers

Assigning event listeners via addEventListener() and removeEventListener()

Intrinsic Events in Web App

Event attributes (onload, onclick, onmouseover, onfocus, onkeyup, onsubmit, onselect): built-in events
Specific attributes are used to bind events to HTML elements

JavaScript Language - The Basics

HTML/CSS only allow for static content and do not allow dynamic interaction
JavaScript is responsible for performing the dynamic behavior of web pages
JavaScript interacts with HTML/CSS content by accessing elements, manipulating their attributes, or performing actions
JavaScript interacts with data from remote HTTP web servers

JavaScript Primitive Types

number, string, boolean, null, undefined
Primitive data types in JavaScript have no methods or behaviors and can't be modified without creating a new type.

JavaScript Variables & Constants

Variable names can use letters, numbers, underscore, and dollar sign. However, it has to begin with a letter or underscore
Local variables are declared with the var keyword in block scope
const declares a constant variable

JavaScript Strings

Strings are series of Unicode characters
Strings in JavaScript are immutable; manipulations create a new string (with concat) instead of modifying the original
Methods include indexOf(), substring(), and others

JavaScript Booleans

Boolean values in JavaScript can be true or false
Falsy values: 0, NaN, "", null, undefined, false
Truthy Values are all other values other than falsy values

JavaScript Null & Undefined

null designates an intentional absence of value (an object)
undefined indicates that a variable is declared but isn't assigned a value.

JavaScript Arrays

Arrays represent ordered collections of values
Arrays are indexed starting from 0
Array methods for adding/removing elements

JavaScript Objects

Objects store key-value pairs
Values are accessed via objectName.propertyName or objectName["propertyName"].

JavaScript Error Objects

Error objects are created when an exception occurs in the JavaScript program
Error objects have properties (attributes): Message (description) and Name (error type)

JavaScript Conditionals & Loops

Conditional statements (if, else if, else) control the execution flow based on conditions
Loop structures (for, while, do...while) repeat sets of expressions

JavaScript Operators & Expressions

Operators perform operations on operands (e.g., arithmetic, comparison, logical)
Special operators exist for checking whether types and values are equal using loose or strict comparisons such as the == and ===.

Comparing Objects

Objects are only equal if they are the same object (a===b)

Declaring and Using Functions

Functions perform specific tasks in JavaScript
Functions in JavaScript are declared using function keyword, optionally including parameters.

Creating Custom Objects

Use the new keyword to create an object instance of a function.

Prototypes

JavaScript objects inherit properties and methods from their prototypes
Prototypes are blueprints for creating objects
Properties and methods of a prototype can be extended without modification affecting other instances

Debugging JavaScript

Write error messages to the browser's development tools console
Use addXToThePage() for debugging directly on the web page

Asynchronous JavaScript

JavaScript is not truly asynchronous
JavaScript programs in a browser environment perform tasks asynchronously using event loop

Asynchronous JavaScript with Callbacks

Functional programming paradigm
Functions are passed as arguments to other functions (callbacks)
Callbacks are executed when a condition is met or an asynchronous event occurs
Events, timers, and network interactions are examples of asynchronous operations

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Description

Test your knowledge on JavaScript methods related to DOM manipulation with this quiz. Explore topics such as creating elements, modifying styles, and event handling. Enhance your understanding of how JavaScript interacts with HTML and the Document Object Model.