Introduction to JavaScript

Frequently Asked Questions

1. What is JavaScript?

   • One of the most popular programming languages in the world.
   • Used by companies like Netflix, Walmart, and PayPal.
   • Average salary for a JavaScript developer in the US is $72,000/year.
   • Opportunities as front-end, back-end, or full stack developer.

2. What can you do with JavaScript?

   • Originally used for building interactive web pages.
   • Now used for building full-blown web/mobile apps, real-time networking apps, command-line tools, and games.

3. Where does JavaScript code run?

   • Initially designed to run in browsers (JavaScript engines like SpiderMonkey for Firefox and V8 for Chrome).
   • Node.js allows JavaScript to run outside browsers on servers.

4. Difference between JavaScript and ECMAScript?

   • ECMAScript is a specification; JavaScript conforms to this specification.
   • ECMAScript standards are maintained by ECMA International.
   • ES6 (released in 2015) introduced many new features.

Writing and Running JavaScript

• JavaScript can be executed in browser consoles or in Node.js.
• Recommended development setup includes Visual Studio Code and Node.js.
• HTML and JavaScript Interaction:
  • Use script tags to run JavaScript in HTML.
  • Script should be placed at the end of body tag for better performance.

Development Tools

• Code Editors:
  • Visual Studio Code, Sublime Text, Atom.
• Node.js:
  • Useful for executing JavaScript outside the browser.

JavaScript Basics

Variables

• Used to store data temporarily.
• Declared using let (for mutable) and const (for immutable).
• Must have meaningful names, cannot start with numbers, use camelCase.

Primitive Types

• Strings, Numbers, Booleans, Undefined, Null.
• JavaScript is a dynamic language; types can change at runtime.

Objects

• Used to group related variables.
• Created using object literals with key-value pairs.
• Access properties using dot or bracket notation.

Arrays

• Data structures to store lists of items.
• Length and type of items can change dynamically.
• Arrays are objects in JavaScript.

Functions

• Blocks of code that perform tasks or calculate values.
• Can have parameters (inputs) and return values.
• Functions can be reused with different arguments.

Additional Concepts

• Dynamic Typing:
  • Type of a variable can change based on the assigned value.
• Type Checking:
  • Use typeof to check variable type.

Summary

• JavaScript enables creating a wide range of applications from web pages to server-side apps.
• Understanding variables, data types, objects, arrays, and functions is crucial for JavaScript programming.
• Tools like Node.js and VS Code enhance development and execution of JavaScript applications.