Introduction to JavaScript

Frequently Asked Questions

What is JavaScript?

• One of the most popular programming languages.
• Used by big companies like Netflix, Walmart, and PayPal.
• Average salary of a JavaScript developer in the US: $72,000/year.
• Roles: Front-end developer, Back-end developer, Full Stack developer.

What can you do with JavaScript?

• Initially used to build interactive web pages.
• Now can be used to build full-blown web/mobile apps, real-time networking applications, command-line tools, and games.
• Huge community support and investments by large companies.

Where does JavaScript code run?

• Originally designed to run only in browsers.
• Each browser has a JavaScript engine (e.g., SpiderMonkey for Firefox, V8 for Chrome).
• Node.js allows JavaScript to run outside of browsers (C++ program including Google’s V8).
• JavaScript can be run inside browsers and in Node.js runtime environment.

Difference between JavaScript and ECMAScript?

• ECMAScript (ES) is a specification JavaScript conforms to.
• Maintained by ECMA organization.
• ECMAScript 2015 (ES6) introduced many new features.

Practical JavaScript

1. Browser JavaScript Console

   • Demonstrates how to use the browser's console to execute JavaScript code.
   • Example: console.log('Hello World');

2. Setting Up Development Environment

   • Tools: Visual Studio Code (VS Code) and Node.js.
   • Instructions on downloading and installing these tools.

3. Basic HTML Integration

   • Create a folder and a new file, index.html.
   • Use boilerplate HTML to host JavaScript code.
   • Install the Live Server extension.
   • Embed JavaScript code using a <script> element.
   • Best practice: Place <script> at the end of the body tag.

4. JavaScript and Node.js

   • Instructions on running JavaScript code in Node.js.
   • VS Code integration for an easier workflow.

JavaScript Fundamentals

Variables

• Use let and const to declare variables. Avoid var.
• Example: let name;, const interestRate = 0.3;
• Rules for naming variables:
  • Cannot be a reserved keyword.
  • Should be meaningful.
  • Cannot start with a number.
  • No spaces or hyphens; use camelCase.
  • Are case-sensitive.

Constants

• Declare constants using const.
• Cannot be reassigned.

Primitive Types

• String: let name = 'Mosh';
• Number: let age = 30;
• Boolean: let isApproved = true;
• Undefined: let firstName; (or explicitly let firstName = undefined;)
• Null: let selectedColor = null;

Dynamic Typing

• JavaScript is a dynamic language; variable types can change at runtime.

Objects

• Group related variables together.
• Created using object literals: let person = { name: 'Mosh', age: 30 };
• Accessing properties: Dot notation (person.name) or Bracket notation (person['name']).

Arrays

• Store lists: let selectedColors = ['red', 'blue'];
• Arrays are dynamic in length and type.
• Accessing elements: selectedColors[0];
• Arrays inherit properties and methods such as .length.

Functions

• A set of statements performing a task or calculating a value.
• Function declaration: function greet(name) { console.log('Hello ' + name); }
• Function call: greet('John');
• Functions with multiple parameters: function greet(firstName, lastName) { ... }
• Returning values: function square(number) { return number * number; }

Best Practices and Tools

• For complex applications, separate JavaScript from HTML for better maintainability.
• Utilize integrated terminal in VS Code for running Node.js scripts directly within the editor.

---

• End with a recommendation to enroll in a comprehensive JavaScript course for further learning.