JavaScript was created by Brendan Eich in 1995 while working at Netscape Communications Corporation.
JavaScript was designed to be a lightweight scripting language for adding interactivity to web pages.
Key Milestones in Its Evolution:
1995: JavaScript 1.0 released with Netscape Navigator 2.0.
1996: Microsoft introduced JScript with Internet Explorer 3.0, leading to cross-browser compatibility issues.
1997: ECMAScript standardization (ECMA-262) by Ecma International to ensure consistency across different implementations.
2024: ECMAScript 2024 (ES15).
Key Features
Dynamic Typing:
JavaScript is dynamically typed, meaning variables can hold values of any type without explicit type declarations.
This flexibility allows for rapid development and prototyping but requires careful handling to avoid type-related errors.
First-class Functions:
Functions in JavaScript are first-class citizens, meaning they can be assigned to variables, passed as arguments to other functions, and returned from functions.
This feature enables powerful programming paradigms such as functional programming and higher-order functions.
Event-driven Programming:
JavaScript is inherently event-driven, allowing developers to write code that responds to user actions, network events, and other asynchronous events.
Event listeners and callbacks are used to handle events and execute code in response to them.
Use Cases
Web Development: Enhancing the interactivity and functionality of web pages through DOM manipulation, form validation, and AJAX requests.
Server-side Scripting: Building scalable and efficient server-side applications using Node.js, Express.js, and other frameworks.
Mobile App Development: Creating cross-platform mobile applications using frameworks like React Native and Ionic.
Desktop App Development: Building desktop applications with Electron, which allows JavaScript, HTML, and CSS to be used for creating native desktop apps.
Game Development: Developing browser-based games using libraries like Phaser and Three.js.
Internet of Things (IoT): Writing JavaScript code for IoT devices using platforms like Node-RED.
JavaScript in a Web Browser
JavaScript can be executed directly in the browser.
You can include JavaScript code in HTML files using the <script> tag.
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>JavaScript Example</title></head><body><h1>Welcome to JavaScript</h1><p>This is a simple example of embedding JavaScript in an HTML document.</p><script>console.log("Hello, World!");</script><!-- You can also link to an external JavaScript file using the <script> tag with the src attribute. --><!-- <script src="script.js"></script> --></body></html>
To open the console in most browsers, press F12 or Ctrl+Shift+I and navigate to the “Console” tab.
On a Server with Node.js
Node.js allows you to run JavaScript on the server-side.
let: Block-scoped, can be updated but not redeclared.
const: Block-scoped, cannot be updated or redeclared.
var name ="Alice";let age =30;const isStudent =true;
var: Function-scoped, can be redeclared and updatedd (avoid using var in modern JavaScript).
Data Types and Values
Primitive Types:
string, number, boolean, null, undefined, symbol
let name ="Alice";// stringlet age =30;// numberlet isStudent =true;// booleanlet unknown =null;// nulllet notDefined;// undefinedlet uniqueId =Symbol("id");// symbol
Reference Types:
object, array, function
let person = { name:"Alice",age:30 };// objectlet numbers = [1,2,3];// arrayfunctiongreet() { console.log("Hello!"); } // function
Differences Between Primitive and Reference Values:
Primitive values are stored directly in the variable.
Reference values store a reference to the memory location where the object is stored.
Comments
Single-line and Multi-line Comments:
Single-line comment: // This is a comment
Multi-line comment: /* This is a multi-line comment */
// This is a single-line commentlet x =10;/* This is a multi-line comment */
Expressions and Statements
Understanding Expressions and Statements:
Expression: Produces a value (e.g., 2 + 2, name = "Alice")
Statement: Performs an action (e.g., let x = 10;, if (x > 5) { ... })
let sum =2+2;// Expressionconsole.log(sum);// Statement
Operators
Arithmetic, Comparison, Logical, and Assignment Operators:
Arithmetic: +, -, *, /, %
Comparison: ==, ===, !=, !==, >, <, >=, <=
Logical: &&, ||, !
Assignment: =, +=, -=, *=, /=
Comparison Operators: == vs ===
== (Equality Operator):
Compares two values for equality after converting both values to a common type (type coercion).
Example:
console.log(5=='5');// Output: true
In the example above, the string '5' is converted to the number 5 before comparison.
=== (Strict Equality Operator):
Compares two values for equality without converting them to a common type (no type coercion).
Example:
console.log(5==='5');// Output: false
In the example above, the comparison returns false because the types of the values are different (number vs. string).
let a =10;let b =5;let sum = a + b;// Arithmeticlet isEqual = (a === b);// Comparisonlet isBothTrue = (a >0&& b >0);// Logicala +=5;// Assignment
Strings
A string is a sequence of characters enclosed in single quotes (') or double quotes ("). It’s a fundamental data type in JavaScript used to represent text.
let str ="Hello, World!";// Length of the stringconsole.log(str.length);// Output: 13// Convert to uppercaseconsole.log(str.toUpperCase());// Output: HELLO, WORLD!// Extract a substringconsole.log(str.slice(7,12));// Output: World// Split the string into an array of wordslet words = str.split(" ");console.log(words);// Output: ["Hello,", "World!"]
String Methods and Properties
Common Methods:
length: Returns the length of the string.
toUpperCase(): Converts the string to uppercase.
toLowerCase(): Converts the string to lowercase.
concat(str1, str2, ...): Concatenates strings.
indexOf(searchValue, fromIndex): Returns the index of the first occurrence of a substring.
lastIndexOf(searchValue, fromIndex): Returns the index of the last occurrence of a substring.
slice(start, end): Extracts a section of a string.
substring(start, end): Extracts a section of a string.
substr(start, length): Extracts a section of a string.
split(separator): Splits a string into an array of substrings.
replace(searchValue, newValue): Replaces occurrences of a substring.
trim(): Removes whitespace from both ends of a string.
charAt(index): Returns the character at a specific index.
charCodeAt(index): Returns the Unicode of the character at a specific index.
String Manipulation Techniques
Concatenation:
let firstName ="John";let lastName ="Doe";let fullName = firstName +" "+ lastName;console.log(fullName);// Output: John Doe
Template Literals (String Interpolation):
let age =30;let message =`My name is ${firstName}${lastName} and I am ${age} years old.`;console.log(message);// Output: My name is John Doe and I am 30 years old.
Using Regular Expressions in JavaScript
Regular expressions (regex) are patterns used to match character combinations in strings. JavaScript provides the RegExp object for working with regular expressions.
Definition: An array is a data structure that can hold multiple values at once. These values can be of any type, including numbers, strings, objects, and even other arrays. Arrays are zero-indexed, meaning the first element is at index 0.
Filtering Elements: Creates a new array with all elements that pass the test implemented by the provided function.
const even = numbers.filter(num => num %2===0);// [2, 4]console.log(even);// Output: [2, 4]
Chaining Methods: Combining multiple array methods to perform complex operations.
const result = numbers.filter(num => num %2===0) // Filter even numbers.map(num => num *2) // Double the filtered numbers.reduce((acc, num) => acc + num,0);// Sum the doubled numbersconsole.log(result);// Output: 12 (2*2 + 4*2)
Objects
Definition of an Object:
An object in JavaScript is a collection of key-value pairs where each key is a string (also called a property name) and each value can be any data type, including other objects. Objects are used to store and manipulate data in a structured way.
Object Creation and Manipulation Techniques:
Creating objects using object literals.
Adding, updating, and deleting properties.
const person = {name:'Alice',age:25};// Adding a propertyperson.job='Developer';// Updating a propertyperson.age=26;// Deleting a propertydelete person.job;console.log(person);// Output: { name: 'Alice', age: 26 }
The Document Object Model (DOM) is a programming interface for HTML and XML documents.
It represents the page’s structure as a tree of nodes.
Each node represents a different part of the document, such as an element, attribute, or text.
Tree Structure of the DOM
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Sample Document</title></head><body><h1>Welcome to the DOM</h1><p>This is a simple HTML document.</p><div id="container"><p class="text">First paragraph</p><p class="text">Second paragraph</p></div></body></html>
graph TD
A[Document]
A --> B[html]
B --> C[head]
C --> D[meta]
D --> D1{{charset=UTF-8}}
C --> E[meta]
E --> E1{{name=viewport}}
E --> E2{{content=width=device-width, initial-scale=1.0}}
C --> F[title]
F --> F1("'Sample Document'")
B --> G[body]
G --> H[h1]
H --> H1("'Welcome to the DOM'")
G --> I[p]
I --> I1("'This is a simple HTML document.'")
G --> J[div]
J --> J1{{id=container}}
J --> K[p]
K --> K1{{class=text}}
K --> K2("'First paragraph'")
J --> L[p]
L --> L1{{class=text}}
L --> L2("'Second paragraph'")
Accessing the DOM
The document object represents the entire HTML document and provides methods and properties for working with the DOM.
The DOM can be accessed and manipulated using JavaScript to create dynamic and interactive web applications.
Common tasks include selecting elements, modifying content, handling events, and creating new elements.
The main methods for selecting elements are getElementById, getElementsByTagName, getElementsByClassName, querySelector, and querySelectorAll.
Selecting Elements (document Object)
// Select the entire documentconst udocumentElement =document;// Select the HTML elementconst htmlElement =document.documentElement;// Select the body elementconst bodyElement =document.body;
Selecting Elements by ID, Tag Name, and Class Name
getElementById: Selects an element by its ID.
getElementsByTagName: Selects elements by their tag name.
getElementsByClassName: Selects elements by their class name.
querySelector: Selects the first element matching a CSS selector.
querySelectorAll: Selects all elements matching a CSS selector.
// Select the first element matching the selectorconst firstElement =document.querySelector('.myClass');// Select all elements matching the selectorconst allElements =document.querySelectorAll('p');
Selecting Elements in JavaScript
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>DOM Selection Example</title></head><body><h1 id="header">Welcome to JavaScript</h1><p class="myClass">This is a paragraph.</p><p class="myClass">This is another paragraph.</p><script>// Select the entire documentconst documentElement =document;// Select the HTML elementconst htmlElement =document.documentElement;// Select the body elementconst bodyElement =document.body;// Select an element by IDconst elementById =document.getElementById('header');console.log(elementById.textContent);// Output: Welcome to JavaScript// Select elements by tag nameconst elementsByTagName =document.getElementsByTagName('p');console.log(elementsByTagName.length);// Output: 2// Select elements by class nameconst elementsByClassName =document.getElementsByClassName('myClass');console.log(elementsByClassName.length);// Output: 2// Select the first element matching the selectorconst firstElement =document.querySelector('.myClass');console.log(firstElement.textContent);// Output: This is a paragraph.// Select all elements matching the selectorconst allElements =document.querySelectorAll('p');console.log(allElements.length);// Output: 2</script></body></html>
Modifying the DOM
The Document Object Model (DOM) can be modified using JavaScript to update the content, structure, and style of web pages.
The main methods for modifying elements are textContent, innerHTML, setAttribute, getAttribute, removeAttribute, createElement, appendChild, insertBefore, and removeChild.
Modifying Element Content:
// Modify text contentelement.textContent='New text';// Modify inner HTMLelement.innerHTML='<strong>Bold text</strong>';
Modifying Element Attributes:
// Set an attributeelement.setAttribute('href','https://example.com');// Get an attribute valueconst hrefValue = element.getAttribute('href');// Remove an attributeelement.removeAttribute('disabled');
Creating New Elements:
const newElement =document.createElement('p');newElement.textContent='This is a new paragraph.';
Adding and Removing Elements:
// Append a child elementparent.appendChild(child);// Insert a child element before anotherparent.insertBefore(newChild, existingChild);// Remove a child elementparent.removeChild(child);
Modifying Element Styles:
// Set a style propertyelement.style.color='red';element.style.fontSize='20px';// Add or remove a classelement.classList.add('myClass');element.classList.remove('myClass');
Understanding Events in JavaScript
Events are actions or occurrences that happen in the browser, such as clicks, key presses, or page loads.
JavaScript can listen for these events and execute code in response.
Event handling involves attaching event listeners to elements to respond to user interactions.
Common events include click, mouseover, keydown, submit, and load.
Event Listeners
Using addEventListener to Handle Events:
The addEventListener method attaches an event handler to an element.
<!DOCTYPE html><html lang="en"><head><meta charset="UTF-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><title>Event Listener Example</title></head><body><!-- A button element that the user can click --><button>Click Me!</button><script>// Select the button elementconst button =document.querySelector('button');// Attach an event listener to the button button.addEventListener('click', () => {// This function will run when the button is clickedalert('Button clicked!'); });</script></body></html>
Default Behavior
Preventing Default Behavior with preventDefault:
Some events have default behaviors (e.g., form submission, link navigation).
The preventDefault method prevents the default action of the event.
const link =document.querySelector('a');link.addEventListener('click', (event) => {event.preventDefault();alert('Link click prevented!');});
Event Propagation
Understanding Event Propagation and Using stopPropagation:
Event propagation determines the order in which event handlers are executed.
Three phases: capturing, target, and bubbling.
The stopPropagation method stops the event from propagating further.
Common form events: submit, change, input, focus, blur.
const form =document.querySelector('form');form.addEventListener('submit', (event) => {event.preventDefault();alert('Form submitted!');});
Working with Dates in JavaScript
JavaScript provides the Date object to work with dates and times. The Date object offers various methods to create, manipulate, and format dates.
Common tasks include creating dates, getting date components, setting date components, formatting dates, and performing date calculations.
Creating Dates
Current Date and Time: javascript const now = new Date(); console.log(now); // Output: current date and time
Specific Date and Time: javascript const specificDate = new Date('2023-10-01T10:00:00'); console.log(specificDate); // Output: Sun Oct 01 2023 10:00:00 GMT+0000 (UTC)
Using Date Components: javascript const dateFromComponents = new Date(2023, 9, 1, 10, 0, 0); // Note: Month is 0-indexed console.log(dateFromComponents); // Output: Sun Oct 01 2023 10:00:00 GMT+0000 (UTC)
Date Methods
Getting Date Components: javascript const date = new Date(); console.log(date.getFullYear()); // Output: 2023 console.log(date.getMonth()); // Output: 9 (October, 0-indexed) console.log(date.getDate()); // Output: 1 console.log(date.getHours()); // Output: current hour console.log(date.getMinutes()); // Output: current minute console.log(date.getSeconds()); // Output: current second
Setting Date Components: javascript const date = new Date(); date.setFullYear(2024); date.setMonth(11); // December date.setDate(25); console.log(date); // Output: Wed Dec 25 2024
Formatting Dates: javascript const date = new Date(); const formattedDate = date.toLocaleDateString('en-US', { year: 'numeric', month: 'long', day: 'numeric' }); console.log(formattedDate); // Output: October 1, 2023
Date Calculations
Adding/Subtracting Time: javascript const date = new Date(); date.setDate(date.getDate() + 7); // Add 7 days console.log(date); // Output: Date 7 days from now
Control structures are used to control the flow of a program based on specified conditions.
Common control structures in JavaScript include if statements, else statements, else if statements, switch statements, and loops.
These structures allow you to make decisions, repeat code, and handle different scenarios in your programs.
Conditional statements are used to perform different actions based on different conditions.
if statement: Executes a block of code if a specified condition is true.
else statement: Executes a block of code if the same condition is false.
switch statement: Evaluates an expression and executes code based on matching case labels.
Conditions in JavaScript
Basic if Statements:
The if statement executes a block of code if a specified condition is true.
Syntax: javascript if (condition) { // code to be executed if condition is true }
let age =18;if (age >=18) {console.log("You are an adult.");}
if…else and else if Conditions
Using if…else Statements:
The if...else statement executes one block of code if a condition is true, and another block if it is false.
Syntax: javascript if (condition) { // code to be executed if condition is true } else { // code to be executed if condition is false }
let age =16;if (age >=18) {console.log("You are an adult.");} else {console.log("You are a minor.");}
Using else if Statements:
The else if statement specifies a new condition to test if the first condition is false.
Syntax: javascript if (condition1) { // code to be executed if condition1 is true } else if (condition2) { // code to be executed if condition2 is true } else { // code to be executed if both conditions are false }
Logical operators (&&, ||, !) are used to combine multiple conditions.
let age =20;let hasID =true;if (age >=18&& hasID) {console.log("You can enter.");} else {console.log("You cannot enter.");}
Type Coercion
Type coercion is the automatic or implicit conversion of values from one data type to another (such as strings to numbers). This can happen in various operations, including comparisons and arithmetic operations.
String to Number: javascript let str = "123"; let num = str - 0; // Implicit conversion to number console.log(num); // Output: 123
Number to String: javascript let num = 123; let str = num + ""; // Implicit conversion to string console.log(str); // Output: "123"
JavaScript automatically converts data types when evaluating conditions. This can lead to unexpected results if not properly understood.
let value ="0";if (value) {console.log("This is true.");} else {console.log("This is false.");}// Output: This is true.
Avoiding Unintended Type Coercion
Use strict equality (===) and inequality (!==) operators to avoid type coercion in comparisons.
let value ="0";if (value ===0) {console.log("This is true.");} else {console.log("This is false.");}// Output: This is false.
Explicit Type Conversion
Convert types explicitly to avoid confusion and ensure the correct type is used.
let str ="123";let num =Number(str);// Explicit conversion to numberconsole.log(num);// Output: 123let num2 =123;let str2 =String(num2);// Explicit conversion to stringconsole.log(str2);// Output: "123"
The switch Statement
Using switch Statements for Multiple Conditions:
The switch statement evaluates an expression and executes code based on matching case labels.
Syntax: javascript switch (expression) { case value1: // code to be executed if expression === value1 break; case value2: // code to be executed if expression === value2 break; default: // code to be executed if no case matches }
let day =3;switch (day) {case1:console.log("Monday");break;case2:console.log("Tuesday");break;case3:console.log("Wednesday");break;default:console.log("Another day");}
Ternary Operation
Using the Ternary Operator for Concise Conditions:
The ternary operator (? :) is a shorthand for if...else statements.
let age =18;let message = age >=18?"You are an adult.":"You are a minor.";console.log(message);// Output: You are an adult.
Short-Circuit Operation
Using Short-Circuit Evaluation in Conditions:
Short-circuit evaluation allows expressions to be evaluated only as necessary.
let isLoggedIn =true;let user = isLoggedIn &&"John Doe";console.log(user);// Output: John Doelet isAdmin =false;let access = isAdmin ||"Access Denied";console.log(access);// Output: Access Denied
Loops
Loops are used to execute a block of code multiple times.
for loop: Executes a block of code a specific number of times.
while loop: Executes a block of code while a specified condition is true.
do...while loop: Executes a block of code at least once and then repeats it while a specified condition is true.
for...of loop: Iterates over the values of an iterable object.
for...in loop: Iterates over the properties of an object.
The for Loop and break/continue Statements
- The `for` loop is used to execute a block of code a specific number of times.
- Syntax:
```javascript
for (initialization; condition; increment) {
// code to be executed
}
```
```javascript
for (let i = 0; i < 5; i++) {
console.log(i); // Output: 0, 1, 2, 3, 4
}
```
Using break and continue Statements
- The `break` statement exits the loop immediately.
- The `continue` statement skips the current iteration and moves to the next one.
```javascript
for (let i = 0; i < 5; i++) {
if (i === 3) {
break; // Exit the loop when i is 3
}
console.log(i); // Output: 0, 1, 2
}
for (let i = 0; i < 5; i++) {
if (i === 3) {
continue; // Skip the iteration when i is 3
}
console.log(i); // Output: 0, 1, 2, 4
}
```
while and do…while Loops
Using while Loops:
The while loop executes a block of code as long as the specified condition is true.
Syntax: javascript while (condition) { // code to be executed }
let i =0;while (i <5) {console.log(i);// Output: 0, 1, 2, 3, 4 i++;}
Using do…while Loops:
The do...while loop executes a block of code once before checking the condition, and then repeats the loop as long as the condition is true.
Syntax: javascript do { // code to be executed } while (condition);
let i =0;do {console.log(i);// Output: 0, 1, 2, 3, 4 i++;} while (i <5);
for…in and for…of Loops
Using for…in Loops:
The for...in loop iterates over the enumerable properties of an object.
Syntax: javascript for (key in object) { // code to be executed }
const person = { name:"Alice",age:30,city:"New York" };for (let key in person) {console.log(key +": "+ person[key]);// Output: name: Alice, age: 30, city: New York}
Using for…of Loops:
The for...of loop iterates over the values of an iterable object (like an array or a string).
Syntax: javascript for (value of iterable) { // code to be executed }
const numbers = [1,2,3,4,5];for (let number of numbers) {console.log(number);// Output: 1, 2, 3, 4, 5}
Functions in JavaScript
Functions are one of the fundamental building blocks in JavaScript. A function is a reusable block of code designed to perform a particular task.
Defining Functions
Function Declaration: javascript function greet(name) { return `Hello, ${name}!`; } console.log(greet('Alice')); // Output: Hello, Alice!
Parameters: Variables listed as a part of the function definition.
Arguments: Values passed to the function when it is invoked.
functionadd(a, b) {return a + b;}console.log(add(2,3));// Output: 5
Default Parameters
Setting Default Values for Parameters: javascript function greet(name = 'Guest') { return `Hello, ${name}!`; } console.log(greet()); // Output: Hello, Guest!
Returning Values
Using the return Statement to Return Values from Functions: javascript function multiply(a, b) { return a * b; } console.log(multiply(4, 5)); // Output: 20
Function Scope
Understanding Local and Global Scope: ```javascript let globalVar = ‘I am global’;
function checkScope() { let localVar = ‘I am local’; console.log(globalVar); // Output: I am global console.log(localVar); // Output: I am local }
checkScope(); console.log(localVar); // Error: localVar is not defined ```
Anonymous Functions
Functions Without a Name: javascript setTimeout(function() { console.log('This is an anonymous function'); }, 1000);
Function Hoisting
Understanding Function Hoisting: ```javascript console.log(hoistedFunction()); // Output: This function is hoisted
function hoistedFunction() { return ‘This function is hoisted’; } ```
Arrow Functions
Using Arrow Functions for Concise Syntax:
Arrow functions provide a shorter syntax for writing function expressions.
Syntax: javascript const functionName = (parameters) => { // code to be executed };
const add = (a, b) => a + b;console.log(add(2,3));// Output: 5
Callback Functions
Functions Passed as Arguments to be Executed Later:
A callback function is a function passed into another function as an argument, which is then invoked inside the outer function.
let name ="Alice";const age =30;const greet = () =>`Hello, ${name}. You are ${age} years old.`;console.log(greet());// Output: Hello, Alice. You are 30 years old.
Promises and Async/Await
Handling Asynchronous Operations:
Promises represent the eventual completion (or failure) of an asynchronous operation.
async and await provide a way to write asynchronous code that looks synchronous.
const fetchData = () => {returnnewPromise((resolve, reject) => {setTimeout(() => {resolve("Data fetched"); },2000); });};asyncfunctiongetData() {const data =awaitfetchData();console.log(data);// Output: Data fetched}getData();
Modules
Using Modules in JavaScript:
Modules allow you to break your code into separate files and import/export functionality.
const person = {name:"Alice",age:30,greet:function() {console.log("Hello, "+this.name); }};person.greet();// Output: Hello, Alice
Prototypes and Inheritance
Understanding Prototypes and Inheritance:
JavaScript uses prototypes for inheritance.
functionPerson(name, age) {this.name= name;this.age= age;}Person.prototype.greet=function() {console.log("Hello, "+this.name);};const alice =newPerson("Alice",30);alice.greet();// Output: Hello, Alice
Classes and Constructors
Using Classes and Constructors for Object-Oriented Programming:
ES6 introduced classes as a syntactical sugar over prototype-based inheritance.
class Person {constructor(name, age) {this.name= name;this.age= age; }greet() {console.log("Hello, "+this.name); }}const alice =newPerson("Alice",30);alice.greet();// Output: Hello, Alice
Asynchronous JavaScript
Callbacks
Using Callbacks for Asynchronous Operations:
Callbacks are functions passed as arguments to be executed later.
```javascript
const numbers = [1, 2, 3, 4, 5];
numbers.push(6); // Add element
numbers.pop(); // Remove last element
numbers.shift(); // Remove first element
numbers.unshift(0); // Add element at the beginning
console.log(numbers); // Output: [0, 2, 3, 4, 5]
```
// module.jsexportconst add = (a, b) => a + b;// main.jsimport { add } from'./module.js';console.log(add(2,3));
Sure! Here’s a detailed outline for your JavaScript lecture slides on Object-Oriented JavaScript:
Object-Oriented JavaScript
Summary
Introduction to Objects: Creating and using objects.
Prototypes and Inheritance: Understanding prototypes and inheritance.
Classes and Constructors: Using classes and constructors for object-oriented programming.
Introduction to Objects
Creating and Using Objects
Objects are collections of key-value pairs.
const person = {name:'Alice',age:25,greet:function() {console.log(`Hello, my name is ${this.name}`); }};person.greet();// Output: Hello, my name is Alice
Prototypes and Inheritance
Understanding Prototypes
Every JavaScript object has a prototype.
Prototypes are used to share properties and methods between objects.
functionPerson(name, age) {this.name= name;this.age= age;}Person.prototype.greet=function() {console.log(`Hello, my name is ${this.name}`);};const alice =newPerson('Alice',25);alice.greet();// Output: Hello, my name is Alice
Inheritance
Objects can inherit properties and methods from other objects.
functionEmployee(name, age, jobTitle) { Person.call(this, name, age);this.jobTitle= jobTitle;}Employee.prototype=Object.create(Person.prototype);Employee.prototype.constructor= Employee;Employee.prototype.work=function() {console.log(`${this.name} is working as a ${this.jobTitle}`);};const bob =newEmployee('Bob',30,'Developer');bob.greet();// Output: Hello, my name is Bobbob.work();// Output: Bob is working as a Developer
Classes and Constructors
Using Classes and Constructors
ES6 introduced classes as a syntactical sugar over JavaScript’s existing prototype-based inheritance.
class Person {constructor(name, age) {this.name= name;this.age= age; }greet() {console.log(`Hello, my name is ${this.name}`); }}class Employee extends Person {constructor(name, age, jobTitle) {super(name, age);this.jobTitle= jobTitle; }work() {console.log(`${this.name} is working as a ${this.jobTitle}`); }}const charlie =newEmployee('Charlie',35,'Manager');charlie.greet();// Output: Hello, my name is Charliecharlie.work();// Output: Charlie is working as a Manager
Sure! Here’s a detailed outline for your JavaScript lecture slides on Asynchronous JavaScript:
Asynchronous JavaScript
Callbacks
Using Callbacks for Asynchronous Operations
A callback is a function passed into another function as an argument, which is then invoked inside the outer function to complete some kind of routine or action.
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