Introduction to JavaScript

FAQs Covered in Lecture

1. What is JavaScript?
2. What can you do with JavaScript?
3. Where does JavaScript code run?
4. What is the difference between JavaScript and ECMAScript?

What is JavaScript?

• Popular programming language
• Used by companies like Netflix, Walmart, and PayPal
• Average salary for JS developers in the US: $72,000/year
• Roles: Front-end Developer, Back-end Developer, Full-Stack Developer

What can you do with JavaScript?

• Historically used for interactive web pages
• Now used for web/mobile apps, real-time networking apps, command-line tools, and games
• Versatile due to community support and investments from companies like Facebook and Google

Where does JavaScript code run?

• Initially designed to run in browsers
  • Examples: Firefox's SpiderMonkey, Chrome's V8
• Can also run outside of browsers using Node.js
  • Node.js: A runtime environment built on Chrome's V8 engine

JavaScript vs. ECMAScript

• ECMAScript: Specification for the language
• JavaScript: Implementation of ECMAScript
• Specification releases: ES6 (2015) and annual updates

Writing and Running JavaScript Code

• Each browser has a JS engine (e.g., Chrome DevTools)
• Example of console.log and alert in browser console
• Developers need a code editor (e.g., Visual Studio Code, Sublime Text)

Setting up Your Development Environment

• Visual Studio Code (VSCode): Recommended code editor
• Node.js: Recommended for running JS code and managing packages
• Live Server extension for VSCode for running web applications

Basics of HTML and JavaScript Integration

• Creating an index.html and adding basic HTML boilerplate
• Adding JavaScript via a <script> element at the end of the body for performance
• Separate JavaScript code into its own file (e.g., index.js)

Variables in JavaScript

• Used to store data temporarily
• Declared using let or const
• Rules for naming variables:
  1. Cannot be reserved keywords.
  2. Should be meaningful.
  3. Cannot start with numbers.
  4. Cannot contain spaces or hyphens; use camelCase.

Constants

• Declared using const
• Value cannot be changed after assignment
• Use const by default unless reassignment is needed

Data Types

Primitive Types

1. String
2. Number
3. Boolean (true/false)
4. Undefined
5. Null

Dynamic Typing

• JavaScript is dynamically typed: a variable's type can change at runtime

Reference Types

1. Objects
   • Collection of key-value pairs
   • Accessed via dot notation or bracket notation
2. Arrays
   • List of items
   • Can store mixed types
   • Accessed via index
3. Functions
   • Set of statements performing a task or calculating a value
   • Can have parameters and return values

Example of JavaScript in Node.js

• Running JavaScript code in Node.js
• Integrated terminal in VSCode for running Node.js
• Node.js is a runtime environment for executing JavaScript code

Functions

1. Declaration: function greets() { }
2. Calling a Function: greets()
3. Parameters and Arguments
4. Returning Values
5. Functional examples for performing tasks and calculations

Conclusion

• Additional resources: Complete JavaScript course with exercises and solutions
• Basics of variables, data types, reference types, and functions covered