Comprehensive Guide to Javascript Basics

Aug 23, 2024

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Javascript Introduction Lecture Notes

Introduction to Javascript

  • Javascript is a web-based interpreted programming language.
  • Used for adding interactive behavior to web pages, building web and mobile apps, creating command line tools, and game development.
  • Not the same as Java, despite the similar name.

Prerequisites

  • HTML and CSS knowledge is helpful but not necessary.
  • You'll need a web browser (Chrome, Firefox, Safari, Opera recommended) and a text editor (Visual Studio Code, Sublime Text, Replit).
    • Avoid using Internet Explorer.

Setting up Visual Studio Code

  • Visit code.visualstudio.com to download.
  • Install the Live Server extension for instant updates in the web browser upon saving.

Basic Setup

  • Create a new folder for your project.
  • Create essential files: index.js (Javascript), index.html, and style.css.
  • Use HTML skeleton code and link CSS and JS files correctly in index.html.

Console and Output

  • Use browser Developer Tools (Inspect -> Console) to view outputs.
  • Use console.log() for displaying output.
  • Use window.alert() for pop-up alerts.

Comments

  • Single-line comments start with //.
  • Multi-line comments are wrapped in /* ... */.

Variables

  • Containers for storing data.
  • Declaring variables: var, let, const (prefer let for variable scope management).
  • Data types include numbers, strings, and booleans.

Arithmetic Expressions

  • Combination of operands and operators.
  • Operators include addition (+), subtraction (-), multiplication (*), division (/), and modulus (%).
  • Augmented assignment operators like +=, -=, etc.

User Input

  • Easy way: window.prompt().
  • HTML text box method for practical applications.

Type Conversion

  • Convert strings to numbers using Number(), numbers to strings using String(), and to booleans using Boolean().
  • Use typeof to check a variable's data type.

Constants

  • Variables that cannot be changed.
  • Declared using const keyword.

Javascript Math

  • Intrinsic object for mathematical functions.
  • Includes Math.round(), Math.floor(), Math.ceil(), Math.pow(), Math.sqrt(), and constants like Math.PI.

Practice Programs

  • Examples include creating a simple counter, random number generator, and calculating the hypotenuse using the Pythagorean theorem.

String Properties and Methods

  • Use properties like length and methods like charAt(), indexOf(), trim(), toUpperCase(), and replaceAll().

Slice and Method Chaining

  • slice() extracts a portion of a string.
  • Method chaining allows multiple method calls on the same object in a single line.

Control Flow

  • If Statements: Execute code based on conditions.
  • Switch Statements: Efficiently compare a value against multiple cases.

Logical Operators

  • And (&&): Both conditions must be true.
  • Or (||): At least one condition must be true.
  • Not (!): Inverts the boolean value.

Loops

  • While Loops: Repeat code while a condition is true.
  • Do While Loops: Execute code once, then repeat while a condition is true.
  • For Loops: Repeat code a specific number of times.
  • Break and Continue: Control loop execution.

Arrays

  • Store multiple values in a single variable.
  • Use methods like push(), pop(), shift(), unshift(), length, and indexOf().

Functions

  • Define reusable blocks of code.
  • Can return values using return.
  • Function expressions and arrow functions as alternatives to traditional functions.

Object-Oriented Programming

  • Objects: Collections of properties and methods.
  • Classes and Constructors: Blueprints for creating objects.
  • Inheritance: Child classes inherit from parent classes.
  • Static Members: Belong to the class, not instances.

Error Handling

  • Use try-catch blocks to manage errors gracefully.
  • throw for user-defined error handling.

Asynchronous Javascript

  • Promises: Handle asynchronous operations.
  • Async/Await: Syntactic sugar for working with promises.

DOM Manipulation

  • Selecting Elements: Use methods like getElementById(), getElementsByClassName(), querySelector(), etc.
  • Traversing and Modifying DOM: Navigate and change elements.

Events

  • Handle user interactions with event listeners and handlers.

Canvas API

  • Draw shapes and text using a 2D context on a canvas.

Games and Projects

  • Examples include Stopwatch, Rock-Paper-Scissors, Tic-Tac-Toe, Snake, and Pong in Javascript.

This summary provides a comprehensive overview of the lecture on Javascript basics, covering essential concepts, tools, and programming techniques necessary for writing Javascript code.