Merge pull request #442 from michaelmjhhhh/michaelmjhhhh-update-mysql-cheatsheet

Add essential sections to MySQL: Alter, Indexes, and Transactions

README.md

@@ -1,21 +1,29 @@
+<div align="center">
+
 [![AWESOME CHEATSHEETS LOGO](_design/cover_github@2x.png)](https://lecoupa.github.io/awesome-cheatsheets/)
 
-<p align=center>
+<a href="https://trendshift.io/repositories/5584" target="_blank">
-     <a href="https://trendshift.io/repositories/5584" target="_blank"><img src="https://trendshift.io/api/badge/repositories/5584" alt="LeCoupa%2Fawesome-cheatsheets | Trendshift" style="width: 250px; height: 55px;" width="250" height="55"/></a>
+  <img src="https://trendshift.io/api/badge/repositories/5584" alt="LeCoupa%2Fawesome-cheatsheets | Trendshift" width="250" height="55"/>
-</p>
+</a>
 
 [![Awesome](https://awesome.re/badge.svg)](https://awesome.re) [![GitHub license](https://img.shields.io/badge/license-MIT-blue.svg)](https://github.com/LeCoupa/awesome-cheatsheets/blob/master/LICENSE)
 
-**WEBSITE DIRECTORY**: [Available here](https://lecoupa.github.io/awesome-cheatsheets/).
+**WEBSITE DIRECTORY**: [Available here](https://lecoupa.github.io/awesome-cheatsheets/)
 
 > 📚 Awesome cheatsheets for popular programming languages, frameworks and development tools. They include everything you should know in one single file.
 
+</div>
+
+---
+
 ## 🤔 Why Awesome-Cheatsheets?
 
 I usually make a cheat sheet when I want to improve my skills in a programming language, a framework or a development tool. [I started doing these kinds of things a long time ago on Gist](https://gist.github.com/LeCoupa). To better keep track of the history and to let people contribute, I re-organized all of them into this single repository. Most of the content is coming from official documentation and some books I have read.
 
 Feel free to take a look. You might learn new things. They have been designed to provide a quick way to assess your knowledge and to save you time.
 
+---
+
 ## 📚 Table of Contents
 
 ### 📃 Languages
@@ -24,46 +32,48 @@ Feel free to take a look. You might learn new things. They have been designed to
 <summary>View cheatsheets</summary>
 
 #### Command line interface
-
 - [Bash](languages/bash.sh)
 
 #### Imperative
-
 - [C](languages/C.txt)
 - [C#](languages/C%23.txt)
 - [Go](languages/golang.md)
 - [Java](languages/java.md)
 - [PHP](languages/php.php)
 - [Python](languages/python.md)
+- [XML](languages/XML.md)
 
 #### Functional
-
 - [JavaScript](languages/javascript.js)
+- [Typescript](languages/typescript.md)
 
 </details>
 
+---
+
 ### 📦 Backend
 
 <details>
 <summary>View cheatsheets</summary>
 
 #### PHP
-
 - [Laravel](backend/laravel.php)
 
 #### Python
-
 - [Django](backend/django.py)
 
-#### Javascript
+#### JavaScript
-
 - [Adonis.js](backend/adonis.js)
 - [Express.js](backend/express.js)
 - [Feathers.js](backend/feathers.js)
 - [Moleculer](backend/moleculer.js)
 - [Node.js](backend/node.js)
 - [Sails.js](backend/sails.js)
-  </details>
+
+</details>
+
+---
+
 
 ### 🌐 Frontend
 
@@ -71,19 +81,20 @@ Feel free to take a look. You might learn new things. They have been designed to
 <summary>View cheatsheets</summary>
 
 #### Basics
-
 - [HTML5](frontend/html5.html)
 - [CSS3](frontend/css3.css)
+- [Typescript](frontend/typescript.ts)
 
 #### Frameworks
-
 - [React.js](frontend/react.js)
 - [Vue.js](frontend/vue.js)
 - [Tailwind.css](frontend/tailwind.css)
 - [Ember.js](frontend/ember.js)
 - [Angular (2+)](frontend/angular.js)
 - [AngularJS](frontend/angularjs.js)
-  </details>
+</details>
+
+---
 
 ### 🗃️ Databases
 
@@ -91,13 +102,15 @@ Feel free to take a look. You might learn new things. They have been designed to
 <summary>View cheatsheets</summary>
 
 #### SQL
-
 - [MySQL](databases/mysql.sh)
 
 #### NoSQL
-
+- [MongoDB](databases/mongodb.sh)
 - [Redis](databases/redis.sh)
-  </details>
+
+</details>
+
+---
 
 ### 🔧 Tools
 
@@ -105,7 +118,6 @@ Feel free to take a look. You might learn new things. They have been designed to
 <summary>View cheatsheets</summary>
 
 #### Development
-
 - [cURL](tools/curl.sh)
 - [Drush](tools/drush.sh)
 - [Elasticsearch](tools/elasticsearch.js)
@@ -118,25 +130,35 @@ Feel free to take a look. You might learn new things. They have been designed to
 - [Xcode](tools/xcode.txt)
 
 #### Infrastructure
-
 - [AWS CLI](tools/aws.sh)
 - [Docker](tools/docker.sh)
+- [GCP CLI](tools/gcp.md)
 - [Heroku CLI](tools/heroku.sh)
 - [Kubernetes](tools/kubernetes.md)
+- [macOS](tools/macos.sh)
 - [Nanobox Boxfile](tools/nanobox_boxfile.yml)
 - [Nanobox CLI](tools/nanobox_cli.sh)
 - [Nginx](tools/nginx.sh)
 - [PM2](tools/pm2.sh)
 - [Ubuntu](tools/ubuntu.sh)
 - [Firebase CLI](tools/firebase_cli.md)
-  </details>
+
+</details>
+
+---
 
 ## 🙌🏼 How to Contribute?
 
 You are more than welcome to contribute and build your own cheat sheet for your favorite programming language, framework or development tool. Just submit changes via pull request and I will review them before merging.
 
+---
+
 ## 👩‍💻👨‍💻 Our valuable Contributors
 
-<p align="center"><a href="https://github.com/LeCoupa/awesome-cheatsheets/graphs/contributors">
+<div align="center">
+
+<a href="https://github.com/LeCoupa/awesome-cheatsheets/graphs/contributors">
   <img src="https://contributors-img.web.app/image?repo=LeCoupa/awesome-cheatsheets" />
-</a></p>
+</a>
+
+</div>

databases/mysql.sh

@@ -82,3 +82,33 @@ SELECT User, Host FROM mysql.user; # List all current MySQL users
 
 SET GLOBAL general_log = 'ON'; # Enable query logging
 SHOW FULL PROCESSLIST; # Show the last queries executed in MySQL
+
+# *****************************************************************************
+# Altering Table Structure
+# *****************************************************************************
+
+ALTER TABLE table_name ADD COLUMN column_name datatype;        # Add a new column to an existing table
+ALTER TABLE table_name MODIFY COLUMN column_name datatype;     # Change the data type of a column
+ALTER TABLE table_name RENAME COLUMN old_name TO new_name;     # Rename a column (MySQL 8.0+)
+ALTER TABLE table_name DROP COLUMN column_name;                # Remove a column from a table
+ALTER TABLE old_table_name RENAME TO new_table_name;           # Rename an entire table
+
+# *****************************************************************************
+# Indexes (Performance Tuning)
+# *****************************************************************************
+
+CREATE INDEX idx_name ON table_name (column_name);             # Create a standard index to speed up queries
+CREATE UNIQUE INDEX idx_name ON table_name (column_name);      # Create a unique index (no duplicate values)
+SHOW INDEX FROM table_name;                                    # List all indexes on a specific table
+DROP INDEX idx_name ON table_name;                             # Remove an index from a table
+EXPLAIN SELECT * FROM table_name WHERE condition;              # Analyze how MySQL executes a query (Check index usage)
+
+# *****************************************************************************
+# Transactions (Data Integrity)
+# *****************************************************************************
+
+START TRANSACTION;                                             # Begin a new transaction
+COMMIT;                                                        # Save all changes made during the transaction
+ROLLBACK;                                                      # Undo all changes if an error occurs before commit
+SET AUTOCOMMIT = 0;                                            # Disable automatic commits for the current session
+SET AUTOCOMMIT = 1;                                            # Re-enable automatic commits after finishing manual transactions

frontend/tailwind.css

@@ -43,11 +43,14 @@
  
  .hidden              /* display: none; */
  .block               /* display: block; */
+ .flow-root           /* display: flow-root; */
  .inline-block        /* display: inline-block; */
  .inline              /* display: inline; */
  .flex                /* display: flex; */
  .inline-flex         /* display: inline-flex; */
  .grid                /* display: grid; */
+ .inline-grid         /* display: inline-grid; */
+ .contents            /* display: contents; */
  .table               /* display: table; */
  .table-caption       /* display: table-caption; */
  .table-cell          /* display: table-cell; */
@@ -68,7 +71,6 @@
  .float-right  /* float: right; */
  .float-left   /* float: left; */
  .float-none   /* float: none; */
- .clearfix     /* &::after { content: ""; display: table; clear: both; } */
  
 /*
  * Clear
@@ -130,8 +132,6 @@
 .overflow-y-visible  /* overflow-y: visible; */
 .overflow-x-scroll   /* overflow-x: scroll; */
 .overflow-y-scroll   /* overflow-y: scroll; */
-.scrolling-touch     /* -webkit-overflow-scrolling: touch; */
-.scrolling-auto      /* -webkit-overflow-scrolling: auto; */
  
 /*
  * Position
@@ -219,7 +219,7 @@
  * By default, only responsive variants are generated for flex-wrap utilities.
  */
 
-.flex-no-wrap       /* flex-wrap: nowrap; */
+.flex-nowrap        /* flex-wrap: nowrap; */
 .flex-wrap          /* flex-wrap: wrap; */
 .flex-wrap-reverse  /* flex-wrap: wrap-reverse; */
 
@@ -478,44 +478,44 @@
 .gap-56      /* gap: 14rem; */
 .gap-64      /* gap: 16rem; */
 .gap-px      /* gap: 1px; */
-.row-gap-0   /* row-gap: 0; */
+.gap-y-0   /* row-gap: 0; */
-.row-gap-1   /* row-gap: 0.25rem; */
+.gap-y-1   /* row-gap: 0.25rem; */
-.row-gap-2   /* row-gap: 0.5rem; */
+.gap-y-2   /* row-gap: 0.5rem; */
-.row-gap-3   /* row-gap: 0.75rem; */
+.gap-y-3   /* row-gap: 0.75rem; */
-.row-gap-4   /* row-gap: 1rem; */
+.gap-y-4   /* row-gap: 1rem; */
-.row-gap-5   /* row-gap: 1.25rem; */
+.gap-y-5   /* row-gap: 1.25rem; */
-.row-gap-6   /* row-gap: 1.5rem; */
+.gap-y-6   /* row-gap: 1.5rem; */
-.row-gap-8   /* row-gap: 2rem; */
+.gap-y-8   /* row-gap: 2rem; */
-.row-gap-10  /* row-gap: 2.5rem; */
+.gap-y-10  /* row-gap: 2.5rem; */
-.row-gap-12  /* row-gap: 3rem; */
+.gap-y-12  /* row-gap: 3rem; */
-.row-gap-16  /* row-gap: 4rem; */
+.gap-y-16  /* row-gap: 4rem; */
-.row-gap-20  /* row-gap: 5rem; */
+.gap-y-20  /* row-gap: 5rem; */
-.row-gap-24  /* row-gap: 6rem; */
+.gap-y-24  /* row-gap: 6rem; */
-.row-gap-32  /* row-gap: 8rem; */
+.gap-y-32  /* row-gap: 8rem; */
-.row-gap-40  /* row-gap: 10rem; */
+.gap-y-40  /* row-gap: 10rem; */
-.row-gap-48  /* row-gap: 12rem; */
+.gap-y-48  /* row-gap: 12rem; */
-.row-gap-56  /* row-gap: 14rem; */
+.gap-y-56  /* row-gap: 14rem; */
-.row-gap-64  /* row-gap: 16rem; */
+.gap-y-64  /* row-gap: 16rem; */
-.row-gap-px  /* row-gap: 1px; */
+.gap-y-px  /* row-gap: 1px; */
-.col-gap-0   /* column-gap: 0; */
+.gap-x-0   /* column-gap: 0; */
-.col-gap-1   /* column-gap: 0.25rem; */
+.gap-x-1   /* column-gap: 0.25rem; */
-.col-gap-2   /* column-gap: 0.5rem; */
+.gap-x-2   /* column-gap: 0.5rem; */
-.col-gap-3   /* column-gap: 0.75rem; */
+.gap-x-3   /* column-gap: 0.75rem; */
-.col-gap-4   /* column-gap: 1rem; */
+.gap-x-4   /* column-gap: 1rem; */
-.col-gap-5   /* column-gap: 1.25rem; */
+.gap-x-5   /* column-gap: 1.25rem; */
-.col-gap-6   /* column-gap: 1.5rem; */
+.gap-x-6   /* column-gap: 1.5rem; */
-.col-gap-8   /* column-gap: 2rem; */
+.gap-x-8   /* column-gap: 2rem; */
-.col-gap-10  /* column-gap: 2.5rem; */
+.gap-x-10  /* column-gap: 2.5rem; */
-.col-gap-12  /* column-gap: 3rem; */
+.gap-x-12  /* column-gap: 3rem; */
-.col-gap-16  /* column-gap: 4rem; */
+.gap-x-16  /* column-gap: 4rem; */
-.col-gap-20  /* column-gap: 5rem; */
+.gap-x-20  /* column-gap: 5rem; */
-.col-gap-24  /* column-gap: 6rem; */
+.gap-x-24  /* column-gap: 6rem; */
-.col-gap-32  /* column-gap: 8rem; */
+.gap-x-32  /* column-gap: 8rem; */
-.col-gap-40  /* column-gap: 10rem; */
+.gap-x-40  /* column-gap: 10rem; */
-.col-gap-48  /* column-gap: 12rem; */
+.gap-x-48  /* column-gap: 12rem; */
-.col-gap-56  /* column-gap: 14rem; */
+.gap-x-56  /* column-gap: 14rem; */
-.col-gap-64  /* column-gap: 16rem; */
+.gap-x-64  /* column-gap: 16rem; */
-.col-gap-px  /* column-gap: 1px; */
+.gap-x-px  /* column-gap: 1px; */
 
 /*
  * Grid Auto Flow
@@ -1153,8 +1153,8 @@
  * By default, only responsive, hover and focus variants are generated for font weight utilities.
  */
 
-.font-hairline   /* font-weight: 100; */
+.font-thin        /* font-weight: 100; */
-.font-thin       /* font-weight: 200; */
+.font-extralight  /* font-weight: 200; */
 .font-light      /* font-weight: 300; */
 .font-normal     /* font-weight: 400; */
 .font-medium     /* font-weight: 500; */
@@ -1479,7 +1479,7 @@
  */
 
 .whitespace-normal    /* white-space: normal; */
-.whitespace-no-wrap   /* white-space: nowrap; */
+.whitespace-nowrap    /* white-space: nowrap; */
 .whitespace-pre       /* white-space: pre; */
 .whitespace-pre-line  /* white-space: pre-line; */
 .whitespace-pre-wrap  /* white-space: pre-wrap; */
@@ -1902,7 +1902,6 @@
  * By default, only responsive, hover and focus variants are generated for box shadow utilities.
  */
 
-.shadow-xs       /* box-shadow: 0 0 0 1px rgba(0, 0, 0, 0.05); */
 .shadow-sm       /* box-shadow: 0 1px 2px 0 rgba(0, 0, 0, 0.05); */
 .shadow          /* box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px 0 rgba(0, 0, 0, 0.06); */
 .shadow-md       /* box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06); */
@@ -1910,9 +1909,34 @@
 .shadow-xl       /* box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04); */
 .shadow-2xl      /* box-shadow: 0 25px 50px -12px rgba(0, 0, 0, 0.25); */
 .shadow-inner    /* box-shadow: inset 0 2px 4px 0 rgba(0, 0, 0, 0.06); */
-.shadow-outline  /* box-shadow: 0 0 0 3px rgba(66, 153, 225, 0.5); */
 .shadow-none     /* box-shadow: none; */
 
+/*
+ * RING
+ * --------------------
+ * Utilities for creating outline rings with box-shadows.
+ * Replaced the old .shadow-outline utility.
+ */
+
+.ring-0    /* box-shadow: 0 0 0 0px; */
+.ring-1    /* box-shadow: 0 0 0 1px; */
+.ring-2    /* box-shadow: 0 0 0 2px; */
+.ring-4    /* box-shadow: 0 0 0 4px; */
+.ring-8    /* box-shadow: 0 0 0 8px; */
+.ring      /* box-shadow: 0 0 0 3px; */
+.ring-inset  /* --ring-inset: inset; */
+
+.ring-transparent  /* --ring-color: transparent; */
+.ring-black        /* --ring-color: #000; */
+.ring-white        /* --ring-color: #fff; */
+.ring-current      /* --ring-color: currentColor; */
+
+.ring-offset-0  /* --ring-offset-width: 0px; */
+.ring-offset-1  /* --ring-offset-width: 1px; */
+.ring-offset-2  /* --ring-offset-width: 2px; */
+.ring-offset-4  /* --ring-offset-width: 4px; */
+.ring-offset-8  /* --ring-offset-width: 8px; */
+
 /*
  * OPACITY
  * --------------------

frontend/typescript.ts

@@ -0,0 +1,670 @@
+/****************************
+ * TYPESCRIPT CHEATSHEET - Quick Reference
+ * Learn more: https://www.typescriptlang.org/docs/
+ * Playground: https://www.typescriptlang.org/play
+ * Handbook: https://www.typescriptlang.org/handbook/
+ *
+ *  Table of contents
+ *  -------------------
+ *  01 | Basic Types
+ *  02 | Variables & Arrays
+ *  03 | Functions
+ *  04 | Objects & Interfaces
+ *  05 | Classes
+ *  06 | Generics
+ *  07 | Union & Literal Types
+ *  08 | Type Guards & Assertions
+ *  09 | Utility Types
+ *  10 | Enums
+ *  11 | Modules
+ *  12 | Advanced Types
+ *  13 | Decorators
+ *  14 | Configuration
+ *  15 | Common Patterns
+ *****************************/
+
+/***************************
+------------ 01: Basic Types -----------
+*******************************/
+
+// Primitive Types
+let str: string = "hello";
+let num: number = 42;
+let bool: boolean = true;
+let undef: undefined = undefined;
+let nul: null = null;
+
+// Special Types
+let anything: any = "can be anything";
+let unknown: unknown = "type-safe any";
+let nothing: void = undefined;
+let never: never = (() => { throw new Error() })();
+
+// Type Inference
+let auto = "TypeScript infers string";
+let nums = [1, 2, 3]; // number[]
+
+/***************************
+------------ 02: Variables & Arrays -----------
+*******************************/
+
+// Arrays
+let numbers: number[] = [1, 2, 3];
+let strings: Array<string> = ["a", "b"];
+let mixed: (string | number)[] = [1, "two"];
+
+// Tuples
+let tuple: [string, number] = ["hello", 42];
+let namedTuple: [name: string, age: number] = ["John", 30];
+
+// Destructuring
+let [first, second] = tuple;
+let [x, y, ...rest] = [1, 2, 3, 4, 5];
+
+// Object Destructuring
+let {name, age} = {name: "John", age: 30};
+let {a: newName, b = 10} = {a: "value"}; // rename & default
+
+/***************************
+------------ 03: Functions -----------
+*******************************/
+
+// Function Declaration
+function add(x: number, y: number): number {
+  return x + y;
+}
+
+// Arrow Functions
+const multiply = (x: number, y: number): number => x * y;
+const greet = (name: string): void => console.log(`Hello ${name}`);
+
+// Optional & Default Parameters
+function build(first: string, last?: string, age = 25): string {
+  return `${first} ${last || ""} (${age})`;
+}
+
+// Rest Parameters
+function sum(...nums: number[]): number {
+  return nums.reduce((a, b) => a + b, 0);
+}
+
+// Function Overloads
+function format(x: string): string;
+function format(x: number): string;
+function format(x: string | number): string {
+  return x.toString();
+}
+
+// Function Types
+type MathOp = (x: number, y: number) => number;
+const divide: MathOp = (x, y) => x / y;
+
+/***************************
+------------ 04: Objects & Interfaces -----------
+*******************************/
+
+// Object Types
+let person: {name: string, age: number} = {name: "John", age: 30};
+
+// Interface
+interface User {
+  readonly id: number;
+  name: string;
+  email?: string; // optional
+  [key: string]: any; // index signature
+}
+
+// Extending Interfaces
+interface Admin extends User {
+  permissions: string[];
+}
+
+// Multiple Inheritance
+interface Timestamped {
+  createdAt: Date;
+}
+interface AdminUser extends User, Timestamped {
+  role: "admin";
+}
+
+// Function in Interface
+interface Calculator {
+  add(x: number, y: number): number;
+  subtract: (x: number, y: number) => number;
+}
+
+/***************************
+------------ 05: Classes -----------
+*******************************/
+
+// Basic Class
+class Animal {
+  public name: string;
+  private age: number;
+  protected species: string;
+  readonly id: number;
+
+  constructor(name: string, age: number) {
+    this.name = name;
+    this.age = age;
+    this.species = "unknown";
+    this.id = Math.random();
+  }
+
+  speak(): void {
+    console.log(`${this.name} makes a sound`);
+  }
+}
+
+// Inheritance
+class Dog extends Animal {
+  breed: string;
+
+  constructor(name: string, age: number, breed: string) {
+    super(name, age);
+    this.breed = breed;
+  }
+
+  speak(): void {
+    console.log(`${this.name} barks`);
+  }
+}
+
+// Abstract Class
+abstract class Shape {
+  abstract area(): number;
+  
+  display(): void {
+    console.log(`Area: ${this.area()}`);
+  }
+}
+
+// Static Members
+class MathUtils {
+  static PI = 3.14159;
+  static circle(radius: number): number {
+    return 2 * MathUtils.PI * radius;
+  }
+}
+
+// Getters/Setters
+class Person {
+  private _age: number = 0;
+
+  get age(): number {
+    return this._age;
+  }
+
+  set age(value: number) {
+    if (value >= 0) this._age = value;
+  }
+}
+
+/***************************
+------------ 06: Generics -----------
+*******************************/
+
+// Generic Functions
+function identity<T>(arg: T): T { return arg; }
+const result = identity<string>("hello");
+const inferred = identity(42); // T inferred as number
+
+// Multiple Type Parameters
+function pair<T, U>(first: T, second: U): [T, U] {
+  return [first, second];
+}
+
+// Generic Interface
+interface Container<T> {
+  value: T;
+  getValue(): T;
+}
+
+// Generic Class
+class Box<T> {
+  contents: T;
+  constructor(value: T) {
+    this.contents = value;
+  }
+}
+
+// Constraints
+interface HasLength {
+  length: number;
+}
+
+function logLength<T extends HasLength>(arg: T): void {
+  console.log(arg.length);
+}
+
+// Keyof Constraint
+function getProperty<T, K extends keyof T>(obj: T, key: K): T[K] {
+  return obj[key];
+}
+
+/***************************
+------------ 07: Union & Literal Types -----------
+*******************************/
+
+// Union Types
+type StringOrNumber = string | number;
+type Status = "loading" | "success" | "error";
+
+function process(id: string | number): void {
+  if (typeof id === "string") {
+    console.log(id.toUpperCase());
+  } else {
+    console.log(id.toFixed(2));
+  }
+}
+
+// Intersection Types
+type Person = {name: string};
+type Employee = {company: string};
+type Staff = Person & Employee; // has both properties
+
+// Literal Types
+type Theme = "light" | "dark";
+type Port = 3000 | 8080 | 9000;
+type Success = true;
+
+// Discriminated Unions
+interface Circle {
+  kind: "circle";
+  radius: number;
+}
+interface Square {
+  kind: "square";
+  sideLength: number;
+}
+type Shape = Circle | Square;
+
+function area(shape: Shape): number {
+  switch (shape.kind) {
+    case "circle":
+      return Math.PI * shape.radius ** 2;
+    case "square":
+      return shape.sideLength ** 2;
+  }
+}
+
+/***************************
+------------ 08: Type Guards & Assertions -----------
+*******************************/
+
+// Type Guards
+function isString(value: any): value is string {
+  return typeof value === "string";
+}
+
+function isNumber(value: any): value is number {
+  return typeof value === "number";
+}
+
+// Using Type Guards
+function process(value: string | number) {
+  if (isString(value)) {
+    console.log(value.toUpperCase()); // TypeScript knows it's string
+  } else {
+    console.log(value.toFixed(2)); // TypeScript knows it's number
+  }
+}
+
+// in operator
+type Fish = { swim: () => void };
+type Bird = { fly: () => void };
+
+function move(animal: Fish | Bird) {
+  if ("swim" in animal) {
+    animal.swim(); // Fish
+  } else {
+    animal.fly(); // Bird
+  }
+}
+
+// instanceof
+function handleError(error: Error | string) {
+  if (error instanceof Error) {
+    console.log(error.message);
+  } else {
+    console.log(error);
+  }
+}
+
+// Type Assertions
+let someValue: any = "hello world";
+let strLength = (someValue as string).length;
+// or: let strLength = (<string>someValue).length;
+
+// Non-null Assertion
+let name: string | null = getName();
+let nameLength = name!.length; // Assert name is not null
+
+/***************************
+------------ 09: Utility Types -----------
+*******************************/
+
+interface Todo {
+  title: string;
+  description: string;
+  completed: boolean;
+}
+
+// Partial<T> - All properties optional
+type PartialTodo = Partial<Todo>;
+// {title?: string, description?: string, completed?: boolean}
+
+// Required<T> - All properties required
+type RequiredTodo = Required<PartialTodo>;
+
+// Readonly<T> - All properties readonly
+type ReadonlyTodo = Readonly<Todo>;
+
+// Pick<T, K> - Select specific properties
+type TodoPreview = Pick<Todo, "title" | "completed">;
+
+// Omit<T, K> - Exclude specific properties
+type TodoInfo = Omit<Todo, "completed">;
+
+// Record<K, T> - Create object type
+type TodoStatus = Record<"pending" | "completed", Todo[]>;
+
+// Exclude<T, U> - Remove types from union
+type NonString = Exclude<string | number | boolean, string>;
+// number | boolean
+
+// Extract<T, U> - Extract types from union
+type StringOnly = Extract<string | number | boolean, string>;
+// string
+
+// NonNullable<T> - Remove null/undefined
+type NonNullString = NonNullable<string | null | undefined>;
+// string
+
+// ReturnType<T> - Get function return type
+function getName(): string { return "John"; }
+type NameType = ReturnType<typeof getName>; // string
+
+// Parameters<T> - Get function parameters as tuple
+type GetNameParams = Parameters<typeof getName>; // []
+
+/***************************
+------------ 10: Enums -----------
+*******************************/
+
+// Numeric Enum
+enum Direction {
+  Up,    // 0
+  Down,  // 1
+  Left,  // 2
+  Right  // 3
+}
+
+// String Enum
+enum Color {
+  Red = "red",
+  Green = "green",
+  Blue = "blue"
+}
+
+// Mixed Enum
+enum Mixed {
+  No = 0,
+  Yes = "yes"
+}
+
+// Const Enum (inlined at compile time)
+const enum StatusCode {
+  OK = 200,
+  NotFound = 404,
+  Error = 500
+}
+
+// Usage
+let currentDirection = Direction.Up;
+let favoriteColor = Color.Blue;
+let status = StatusCode.OK;
+
+/***************************
+------------ 11: Modules -----------
+*******************************/
+
+// Named Exports
+export const PI = 3.14159;
+export function calculate(r: number): number {
+  return PI * r * r;
+}
+export class Calculator {
+  add(x: number, y: number): number { return x + y; }
+}
+
+// Default Export
+export default class Logger {
+  log(message: string): void {
+    console.log(message);
+  }
+}
+
+// Re-exports
+export { Calculator as Calc } from "./calculator";
+export * from "./utilities";
+
+// Import
+import Logger from "./logger";           // default import
+import { PI, calculate } from "./math";  // named imports
+import * as MathUtils from "./math";     // namespace import
+import { Calculator as Calc } from "./calculator"; // alias
+
+// Dynamic Imports
+const module = await import("./dynamic-module");
+
+/***************************
+------------ 12: Advanced Types -----------
+*******************************/
+
+// Mapped Types
+type Nullable<T> = {
+  [P in keyof T]: T[P] | null;
+};
+
+type OptionalId<T> = {
+  [P in keyof T]: P extends "id" ? T[P] | undefined : T[P];
+};
+
+// Conditional Types
+type IsString<T> = T extends string ? true : false;
+type StringCheck = IsString<"hello">; // true
+
+// Template Literal Types
+type EventName<T extends string> = `on${Capitalize<T>}`;
+type ClickEvent = EventName<"click">; // "onClick"
+
+// Indexed Access Types
+type Person = { name: string; age: number; location: string };
+type PersonName = Person["name"]; // string
+type PersonKeys = keyof Person;   // "name" | "age" | "location"
+
+// Recursive Types
+type Json = string | number | boolean | null | Json[] | {[key: string]: Json};
+
+/***************************
+------------ 13: Decorators -----------
+*******************************/
+
+// Class Decorator
+function Component(name: string) {
+  return function<T extends {new(...args: any[]): {}}>(constructor: T) {
+    return class extends constructor {
+      componentName = name;
+    };
+  };
+}
+
+@Component("MyComponent")
+class MyClass {}
+
+// Method Decorator
+function Log(target: any, propertyName: string, descriptor: PropertyDescriptor) {
+  const method = descriptor.value;
+  descriptor.value = function(...args: any[]) {
+    console.log(`Calling ${propertyName} with`, args);
+    return method.apply(this, args);
+  };
+}
+
+class Service {
+  @Log
+  getData(): string {
+    return "data";
+  }
+}
+
+// Property Decorator
+function MinLength(length: number) {
+  return function(target: any, propertyName: string) {
+    let value: string;
+    
+    const getter = () => value;
+    const setter = (newVal: string) => {
+      if (newVal.length < length) {
+        throw new Error(`${propertyName} must be at least ${length} chars`);
+      }
+      value = newVal;
+    };
+    
+    Object.defineProperty(target, propertyName, {
+      get: getter,
+      set: setter
+    });
+  };
+}
+
+class User {
+  @MinLength(3)
+  username: string;
+}
+
+/***************************
+------------ 14: Configuration -----------
+*******************************/
+
+// tsconfig.json
+/*
+{
+  "compilerOptions": {
+    "target": "ES2020",
+    "module": "commonjs",
+    "lib": ["ES2020", "DOM"],
+    "outDir": "./dist",
+    "rootDir": "./src",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "moduleResolution": "node",
+    "allowSyntheticDefaultImports": true,
+    "experimentalDecorators": true,
+    "emitDecoratorMetadata": true,
+    "sourceMap": true,
+    "declaration": true,
+    "removeComments": true,
+    "noImplicitAny": true,
+    "noImplicitReturns": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true
+  },
+  "include": ["src/**/*"],
+  "exclude": ["node_modules", "dist"]
+}
+*/
+
+// Compiler Options Quick Reference
+// --target: ES5, ES6, ES2017, ES2018, ES2019, ES2020, ESNext
+// --module: commonjs, amd, es2015, es2020, esnext, system, umd
+// --lib: ES5, ES6, ES2017, DOM, WebWorker, ScriptHost
+// --strict: Enable all strict type checking options
+
+/***************************
+------------ 15: Common Patterns -----------
+*******************************/
+
+// API Response Type
+interface ApiResponse<T> {
+  data: T;
+  status: number;
+  message: string;
+}
+
+// Event Handler Pattern
+type EventHandler<T = Event> = (event: T) => void;
+const onClick: EventHandler<MouseEvent> = (e) => console.log(e.clientX);
+
+// Builder Pattern
+class QueryBuilder {
+  private query = "";
+  
+  select(fields: string): this {
+    this.query += `SELECT ${fields} `;
+    return this;
+  }
+  
+  from(table: string): this {
+    this.query += `FROM ${table} `;
+    return this;
+  }
+  
+  build(): string {
+    return this.query.trim();
+  }
+}
+
+// Factory Pattern
+interface Shape { area(): number; }
+class Circle implements Shape {
+  constructor(private radius: number) {}
+  area(): number { return Math.PI * this.radius ** 2; }
+}
+
+class ShapeFactory {
+  static createCircle(radius: number): Shape {
+    return new Circle(radius);
+  }
+}
+
+// Promise/Async Patterns
+type AsyncResult<T> = Promise<T | Error>;
+
+async function fetchUser(id: number): Promise<User | null> {
+  try {
+    const response = await fetch(`/api/users/${id}`);
+    return await response.json();
+  } catch {
+    return null;
+  }
+}
+
+// Type-safe Environment Variables
+interface Env {
+  NODE_ENV: "development" | "production" | "test";
+  PORT: number;
+  DATABASE_URL: string;
+}
+
+declare global {
+  namespace NodeJS {
+    interface ProcessEnv extends Env {}
+  }
+}
+
+/*
+ * QUICK TIPS
+ * ----------
+ * • Use 'unknown' instead of 'any' when possible
+ * • Prefer 'interface' for object shapes, 'type' for unions/computed types
+ * • Enable strict mode in tsconfig.json
+ * • Use const assertions: const colors = ['red', 'blue'] as const
+ * • Prefer type guards over type assertions
+ * • Use utility types instead of manual type manipulation
+ * • Enable noImplicitAny for better type safety
+ * • Use discriminated unions for complex state management
+ */

languages/typescript.md

@@ -0,0 +1,815 @@
+# TypeScript
+
+* TypeScript is a statically typed superset of JavaScript that compiles to plain JavaScript
+
+* It adds optional static type definitions to JavaScript, enabling better tooling and error detection
+
+* In TypeScript, types are checked at compile-time, not runtime
+
+* A TypeScript file has an extension of .ts (or .tsx for React components)
+
+* TypeScript follows JavaScript syntax but adds type annotations and advanced features
+
+* We can compile and run a TypeScript file by the following commands:
+
+    `$ tsc filename.ts` (compile to JavaScript)
+    `$ node filename.js` (run the compiled JavaScript)
+    
+    Or directly: `$ ts-node filename.ts`
+
+#### TypeScript requires compilation to JavaScript before execution.
+
+## Create and execute a program
+
+1. Install TypeScript globally: `npm install -g typescript`
+1. Create the program: `touch program.ts`
+1. Write the TypeScript code and save it
+1. Compile: `tsc program.ts`
+1. Run: `node program.js`
+
+<br>
+
+### Basic Data Types
+
+| Data Type | Description | Example |
+| --------- | ----------- | ------- |
+| number | Integer and floating point values | `42`, `3.14`, `-7` |
+| string | Text values | `"hello"`, `'world'`, `` `template` `` |
+| boolean | True/false values | `true`, `false` |
+| undefined | Undefined value | `undefined` |
+| null | Null value | `null` |
+| any | Any type (disables type checking) | Can be anything |
+| unknown | Type-safe counterpart of any | Requires type checking |
+| void | Absence of any type | Function return type |
+| never | Type that never occurs | Functions that throw errors |
+| object | Non-primitive types | `{}`, `[]`, functions |
+
+<br>
+
+## Keywords and Reserved Words
+<br>
+
+- TypeScript includes all JavaScript keywords plus additional TypeScript-specific ones
+
+| Keyword | Description  | Category |
+|---------- | ---------- | --------- |
+| let | Declares a block-scoped variable | Variable Declaration |
+| const | Declares a block-scoped constant | Variable Declaration |
+| var | Declares a function-scoped variable | Variable Declaration |
+| function | Declares a function | Function |
+| class | Declares a class | Class |
+| interface | Declares an interface | Type Definition |
+| type | Declares a type alias | Type Definition |
+| enum | Declares an enumeration | Type Definition |
+| namespace | Declares a namespace | Module System |
+| module | Declares a module | Module System |
+| import | Imports from another module | Module System |
+| export | Exports from current module | Module System |
+| extends | Class/interface inheritance | Inheritance |
+| implements | Class implements interface | Inheritance |
+| public | Public access modifier | Access Modifier |
+| private | Private access modifier | Access Modifier |
+| protected | Protected access modifier | Access Modifier |
+| readonly | Read-only property | Access Modifier |
+| static | Static class member | Class Member |
+| abstract | Abstract class/method | Class |
+| async | Asynchronous function | Async Programming |
+| await | Awaits a promise | Async Programming |
+| new | Creates new instance | Object Creation |
+| this | Current object reference | Object Reference |
+| super | Parent class reference | Inheritance |
+| typeof | Gets type of variable | Type Operation |
+| keyof | Gets keys of type | Type Operation |
+| in | Property existence check | Type Guard |
+| instanceof | Instance type check | Type Guard |
+| as | Type assertion | Type Assertion |
+| is | Type predicate | Type Guard |
+| infer | Infers type in conditional types | Advanced Types |
+| declare | Ambient declarations | Declaration |
+| get | Property getter | Accessor |
+| set | Property setter | Accessor |
+| yield | Generator yield | Generator |
+
+<br>
+
+## Operators
+
+<br>
+
+| Operator | Description |
+|-|-|
+|  ( )	|  Grouping, function call, type assertion |
+|  [ ]	|  Array indexing, array/tuple types |
+|  .	|  Property access |
+|  ?.   | 	Optional chaining |
+| !   |	Non-null assertion, logical not |
+|  ~   | 	Bitwise not |
+| \-   |	Unary minus, arithmetic subtraction |
+|  \+   | 	Unary plus, arithmetic addition |
+|  \*   |	Multiplication |
+|  /   	| Division |
+|  %    |	Modulo |
+|  \*\* | Exponentiation |
+| <<   | Left shift |
+| \>>   |	Right shift |
+| \>>>   |	Unsigned right shift |
+ | <    |	Less than |
+| <=   |	Less than or equal |
+| \>    |	Greater than |
+| \>=   |	Greater than or equal |
+|  ==   |	Equality (with coercion) |
+|  ===   |	Strict equality |
+| !=  | 	Inequality (with coercion) |
+| !==  | 	Strict inequality |
+|  & | Bitwise AND |
+| ^ | Bitwise XOR |
+| \| | Bitwise OR, Union types |
+|  && | Logical AND |
+| \|\| | Logical OR |
+| ??   | Nullish coalescing |
+| ? :  | Ternary conditional |
+| =  | Assignment |
+|  += | Add and assign |
+|  -=  | Subtract and assign |
+|  *= | Multiply and assign |
+|  /= | Divide and assign |
+|  %= | Modulo and assign |
+| **= | Exponentiate and assign |
+| <<= | Left shift and assign |
+|  \>>= | Right shift and assign |
+|  &= | Bitwise AND and assign |
+|  ^= | Bitwise XOR and assign |
+|  \|= | Bitwise OR and assign |
+|  , | Comma operator |
+| => | Arrow function |
+| ... | Spread/rest operator |
+
+### Basic Data Structures
+
+### Array
+
+- Array is an ordered collection of elements of the same or different types.
+
+- Arrays are created using square brackets or Array constructor:
+
+```typescript
+let numbers: number[] = [1, 2, 3, 4];
+let fruits: Array<string> = ["apple", "banana", "cherry"];
+let mixed: (string | number)[] = [1, "two", 3];
+```
+
+- Array elements are indexed starting from 0.
+
+- Arrays are mutable - you can change, add, and remove elements.
+
+- Common array methods:
+```typescript
+let arr = [1, 2, 3];
+arr.push(4);        // Add to end: [1, 2, 3, 4]
+arr.pop();          // Remove from end: [1, 2, 3]
+arr.unshift(0);     // Add to start: [0, 1, 2, 3]
+arr.shift();        // Remove from start: [1, 2, 3]
+arr.length;         // Get length: 3
+```
+
+### Tuple
+
+- Tuple is an array with a fixed number of elements of specific types.
+
+- Tuples are created using square brackets with type annotations:
+```typescript
+let person: [string, number] = ["John", 30];
+let coordinate: [number, number] = [10, 20];
+```
+
+- Tuple elements are ordered and have specific types at each position.
+
+- You can access elements by index, but type checking ensures correctness:
+```typescript
+let point: [number, number] = [10, 20];
+console.log(point[0]); // 10 (number)
+console.log(point[1]); // 20 (number)
+```
+
+- Named tuples provide better readability:
+```typescript
+let user: [name: string, age: number] = ["Alice", 25];
+```
+
+- Optional and rest elements in tuples:
+```typescript
+let optional: [string, number?] = ["hello"];
+let rest: [string, ...number[]] = ["coords", 1, 2, 3];
+```
+
+### Set
+
+- Set is a collection of unique values of any type.
+
+- Sets are created using the Set constructor:
+```typescript
+let uniqueNumbers = new Set<number>([1, 2, 3, 2]); // {1, 2, 3}
+let stringSet = new Set<string>();
+```
+
+- Set operations:
+```typescript
+let mySet = new Set<string>();
+mySet.add("apple");     // Add element
+mySet.has("apple");     // Check existence: true
+mySet.delete("apple");  // Remove element
+mySet.clear();          // Remove all elements
+mySet.size;             // Get size
+```
+
+- Iterating over Set:
+```typescript
+let fruits = new Set(["apple", "banana", "cherry"]);
+for (let fruit of fruits) {
+    console.log(fruit);
+}
+```
+
+### Map
+
+- Map is a collection of key-value pairs where keys can be any type.
+
+- Maps are created using the Map constructor:
+```typescript
+let userMap = new Map<string, number>();
+let mixedMap = new Map<string | number, any>();
+```
+
+- Map operations:
+```typescript
+let map = new Map<string, number>();
+map.set("age", 30);         // Add key-value pair
+map.get("age");             // Get value: 30
+map.has("age");             // Check key exists: true
+map.delete("age");          // Remove key-value pair
+map.clear();                // Remove all entries
+map.size;                   // Get size
+```
+
+- Object vs Map:
+```typescript
+// Object - string/symbol keys only
+let obj: { [key: string]: number } = { "age": 30 };
+
+// Map - any type keys
+let map = new Map<any, number>();
+map.set("age", 30);
+map.set(42, 100);
+map.set(true, 1);
+```
+
+### Object Types and Interfaces
+
+- Objects store key-value pairs and are fundamental to TypeScript.
+
+- Object type annotation:
+```typescript
+let person: { name: string; age: number } = {
+    name: "John",
+    age: 30
+};
+```
+
+- Interface definition for better reusability:
+```typescript
+interface User {
+    readonly id: number;    // Read-only property
+    name: string;
+    age?: number;          // Optional property
+    [key: string]: any;    // Index signature
+}
+
+let user: User = {
+    id: 1,
+    name: "Alice"
+};
+```
+
+- Nested objects and complex types:
+```typescript
+interface Address {
+    street: string;
+    city: string;
+    country: string;
+}
+
+interface Person {
+    name: string;
+    address: Address;
+    hobbies: string[];
+}
+```
+
+### Conditional branching
+
+```typescript
+// If-else statements
+if (condition) {
+    // code block
+} else if (anotherCondition) {
+    // code block
+} else {
+    // code block
+}
+
+// Ternary operator
+let result = condition ? valueIfTrue : valueIfFalse;
+
+// Switch statement
+switch (variable) {
+    case value1:
+        // code
+        break;
+    case value2:
+        // code
+        break;
+    default:
+        // code
+        break;
+}
+```
+
+### Loops
+
+TypeScript supports all JavaScript loop constructs:
+
+#### For loop
+```typescript
+// Traditional for loop
+for (let i = 0; i < 5; i++) {
+    console.log(i);
+}
+
+// For-of loop (iterates over values)
+let fruits = ["apple", "banana", "cherry"];
+for (let fruit of fruits) {
+    console.log(fruit);
+}
+
+// For-in loop (iterates over keys/indices)
+for (let index in fruits) {
+    console.log(index, fruits[index]);
+}
+```
+
+#### While loop
+```typescript
+let i = 0;
+while (i < 5) {
+    console.log(i);
+    i++;
+}
+
+// Do-while loop
+let j = 0;
+do {
+    console.log(j);
+    j++;
+} while (j < 5);
+```
+
+#### Loop control
+```typescript
+for (let i = 0; i < 10; i++) {
+    if (i === 3) continue;  // Skip iteration
+    if (i === 7) break;     // Exit loop
+    console.log(i);
+}
+```
+
+### Function definition
+
+```typescript
+// Function declaration
+function functionName(param1: type, param2: type): returnType {
+    return value;
+}
+
+// Function expression
+const functionName = function(param: type): returnType {
+    return value;
+};
+
+// Arrow function
+const functionName = (param: type): returnType => {
+    return value;
+};
+
+// Arrow function (concise)
+const functionName = (param: type): returnType => value;
+```
+
+### Function variations
+
+```typescript
+// Optional parameters
+function greet(name: string, age?: number): string {
+    return age ? `Hello ${name}, you are ${age}` : `Hello ${name}`;
+}
+
+// Default parameters
+function multiply(a: number, b: number = 1): number {
+    return a * b;
+}
+
+// Rest parameters
+function sum(...numbers: number[]): number {
+    return numbers.reduce((total, num) => total + num, 0);
+}
+
+// Function overloads
+function process(input: string): string;
+function process(input: number): number;
+function process(input: string | number): string | number {
+    if (typeof input === 'string') {
+        return input.toUpperCase();
+    }
+    return input * 2;
+}
+
+// Generic functions
+function identity<T>(arg: T): T {
+    return arg;
+}
+
+let result = identity<string>("hello"); // Type is string
+let result2 = identity(42);             // Type inferred as number
+```
+
+### Function call
+
+```typescript
+functionName(argument1, argument2);
+
+// With optional parameters
+greet("John");          // "Hello John"
+greet("John", 25);      // "Hello John, you are 25"
+
+// With rest parameters
+sum(1, 2, 3, 4);        // 10
+
+// Generic function call
+identity<string>("hello");
+identity(42);           // Type inferred
+```
+
+### Classes
+
+```typescript
+class ClassName {
+    // Properties
+    public publicProperty: type;
+    private privateProperty: type;
+    protected protectedProperty: type;
+    readonly readonlyProperty: type;
+    static staticProperty: type;
+
+    // Constructor
+    constructor(param: type) {
+        this.publicProperty = param;
+    }
+
+    // Methods
+    public method(): returnType {
+        return value;
+    }
+
+    // Getters and setters
+    get property(): type {
+        return this.privateProperty;
+    }
+
+    set property(value: type) {
+        this.privateProperty = value;
+    }
+
+    // Static method
+    static staticMethod(): returnType {
+        return value;
+    }
+}
+
+// Inheritance
+class ChildClass extends ParentClass {
+    constructor(param: type) {
+        super(param); // Call parent constructor
+    }
+
+    // Override method
+    method(): returnType {
+        return super.method(); // Call parent method
+    }
+}
+
+// Abstract class
+abstract class AbstractClass {
+    abstract abstractMethod(): void;
+    
+    concreteMethod(): void {
+        console.log("This is implemented");
+    }
+}
+```
+
+### Key TypeScript Features
+
+* **Static Typing**: Types are checked at compile-time
+* **Type Inference**: TypeScript can often infer types automatically
+* **Optional Typing**: You can gradually add types to existing JavaScript
+* **Generics**: Create reusable components that work with multiple types
+* **Interfaces**: Define contracts for objects and classes
+* **Enums**: Create named constants
+* **Union Types**: Variables can be one of several types
+* **Intersection Types**: Combine multiple types
+* **Type Guards**: Runtime type checking
+* **Decorators**: Add metadata to classes and methods
+
+### Compilation
+
+* TypeScript code must be compiled to JavaScript before execution
+* The TypeScript compiler (`tsc`) performs type checking and transpilation
+* Configuration is managed through `tsconfig.json`
+* TypeScript can target different JavaScript versions (ES5, ES6, etc.)
+* Source maps can be generated for debugging compiled code
+
+#### Sample TypeScript Code
+
+**hello.ts**
+```typescript
+// TypeScript source code
+interface User {
+    name: string;
+    age: number;
+    isActive?: boolean;
+}
+
+class UserManager {
+    private users: User[] = [];
+
+    addUser(user: User): void {
+        this.users.push(user);
+        console.log(`Added user: ${user.name}`);
+    }
+
+    getActiveUsers(): User[] {
+        return this.users.filter(user => user.isActive ?? true);
+    }
+
+    getUserCount(): number {
+        return this.users.length;
+    }
+}
+
+// Generic function
+function processData<T>(data: T[], processor: (item: T) => T): T[] {
+    return data.map(processor);
+}
+
+// Usage
+const userManager = new UserManager();
+
+const newUser: User = {
+    name: "John Doe",
+    age: 30,
+    isActive: true
+};
+
+userManager.addUser(newUser);
+
+// Arrow functions with types
+const formatUser = (user: User): string => 
+    `${user.name} (${user.age} years old)`;
+
+// Union types and type guards
+function displayInfo(value: string | number | boolean): string {
+    if (typeof value === "string") {
+        return `Text: ${value.toUpperCase()}`;
+    } else if (typeof value === "number") {
+        return `Number: ${value.toFixed(2)}`;
+    } else {
+        return `Boolean: ${value ? "Yes" : "No"}`;
+    }
+}
+
+console.log(displayInfo("hello"));
+console.log(displayInfo(42.567));
+console.log(displayInfo(true));
+```
+
+#### Compilation Commands
+
+```bash
+# Compile single file
+tsc hello.ts
+
+# Compile with specific target
+tsc hello.ts --target ES2020
+
+# Compile with source maps
+tsc hello.ts --sourceMap
+
+# Watch mode (recompile on changes)
+tsc hello.ts --watch
+
+# Compile all files in project
+tsc
+
+# Check for errors without generating files
+tsc --noEmit
+
+# Compile with strict mode
+tsc hello.ts --strict
+```
+
+#### Compiled JavaScript Output
+
+**hello.js** (compiled from above TypeScript)
+```javascript
+"use strict";
+// JavaScript output (target ES2017)
+class UserManager {
+    constructor() {
+        this.users = [];
+    }
+    addUser(user) {
+        this.users.push(user);
+        console.log(`Added user: ${user.name}`);
+    }
+    getActiveUsers() {
+        return this.users.filter(user => user.isActive ?? true);
+    }
+    getUserCount() {
+        return this.users.length;
+    }
+}
+// Generic function (types removed)
+function processData(data, processor) {
+    return data.map(processor);
+}
+// Usage
+const userManager = new UserManager();
+const newUser = {
+    name: "John Doe",
+    age: 30,
+    isActive: true
+};
+userManager.addUser(newUser);
+// Arrow functions
+const formatUser = (user) => `${user.name} (${user.age} years old)`;
+// Type guards remain as runtime checks
+function displayInfo(value) {
+    if (typeof value === "string") {
+        return `Text: ${value.toUpperCase()}`;
+    }
+    else if (typeof value === "number") {
+        return `Number: ${value.toFixed(2)}`;
+    }
+    else {
+        return `Boolean: ${value ? "Yes" : "No"}`;
+    }
+}
+console.log(displayInfo("hello"));
+console.log(displayInfo(42.567));
+console.log(displayInfo(true));
+```
+
+#### tsconfig.json Configuration
+
+```json
+{
+  "compilerOptions": {
+    // Basic Options
+    "target": "ES2020",                     // Target JavaScript version
+    "module": "commonjs",                   // Module system
+    "lib": ["ES2020", "DOM"],              // Include library files
+    "outDir": "./dist",                     // Output directory
+    "rootDir": "./src",                     // Input directory
+    "strict": true,                         // Enable strict type checking
+    
+    // Additional Checks
+    "noUnusedLocals": true,                // Error on unused variables
+    "noUnusedParameters": true,            // Error on unused parameters
+    "noImplicitReturns": true,             // Error on missing return statements
+    "noFallthroughCasesInSwitch": true,    // Error on fallthrough cases
+    
+    // Module Resolution
+    "moduleResolution": "node",             // Module resolution strategy
+    "baseUrl": "./",                        // Base directory
+    "paths": {                              // Path mapping
+      "@/*": ["src/*"],
+      "@utils/*": ["src/utils/*"]
+    },
+    
+    // Source Maps & Debugging
+    "sourceMap": true,                      // Generate source maps
+    "inlineSourceMap": false,               // Don't inline source maps
+    "declaration": true,                    // Generate .d.ts files
+    "declarationMap": true,                 // Generate .d.ts.map files
+    
+    // Experimental
+    "experimentalDecorators": true,         // Enable decorators
+    "emitDecoratorMetadata": true,          // Emit decorator metadata
+    
+    // JavaScript Support
+    "allowJs": true,                        // Allow JavaScript files
+    "checkJs": false,                       // Type check JavaScript files
+    
+    // Other Options
+    "esModuleInterop": true,               // CommonJS/ES6 interop
+    "skipLibCheck": true,                  // Skip lib.d.ts type checking
+    "forceConsistentCasingInFileNames": true, // Consistent file names
+    "removeComments": true,                // Remove comments from output
+    "noEmitOnError": true                  // Don't emit if there are errors
+  },
+  "include": [
+    "src/**/*",                           // Include all files in src
+    "tests/**/*"                          // Include test files
+  ],
+  "exclude": [
+    "node_modules",                       // Exclude node_modules
+    "dist",                               // Exclude output directory
+    "**/*.test.ts",                       // Exclude test files from compilation
+    "**/*.spec.ts"
+  ],
+  "files": [
+    // Explicitly include specific files (optional)
+    "src/main.ts"
+  ]
+}
+```
+
+#### Package.json Scripts
+
+```json
+{
+  "name": "typescript-project",
+  "version": "1.0.0",
+  "scripts": {
+    "build": "tsc",
+    "start": "node dist/main.js",
+    "dev": "ts-node src/main.ts",
+    "watch": "tsc --watch",
+    "clean": "rm -rf dist",
+    "type-check": "tsc --noEmit"
+  },
+  "devDependencies": {
+    "typescript": "^4.9.0",
+    "ts-node": "^10.9.0",
+    "@types/node": "^18.0.0"
+  }
+}
+```
+
+#### Compilation Examples with Different Targets
+
+**Original TypeScript:**
+```typescript
+const greet = (name: string = "World"): string => `Hello, ${name}!`;
+const user = { name: "Alice", age: 30 };
+const { name, age } = user;
+```
+
+**Compiled to ES5:**
+```javascript
+var greet = function (name) {
+    if (name === void 0) { name = "World"; }
+    return "Hello, " + name + "!";
+};
+var user = { name: "Alice", age: 30 };
+var name = user.name, age = user.age;
+```
+
+**Compiled to ES2020:**
+```javascript
+const greet = (name = "World") => `Hello, ${name}!`;
+const user = { name: "Alice", age: 30 };
+const { name, age } = user;
+```
+
+#### Error Examples
+
+**TypeScript with errors:**
+```typescript
+// Type errors that prevent compilation
+let message: string = 42;              // Error: Type 'number' is not assignable to type 'string'
+let numbers: number[] = ["a", "b"];    // Error: Type 'string' is not assignable to type 'number'
+
+function add(a: number, b: number): number {
+    return a + b;
+}
+
+add("hello", "world");                 // Error: Argument of type 'string' is not assignable to parameter of type 'number'
+```
+
+**Compiler output:**
+```bash
+$ tsc error-example.ts
+error-example.ts(2,5): error TS2322: Type 'number' is not assignable to type 'string'.
+error-example.ts(3,5): error TS2322: Type 'string[]' is not assignable to type 'number[]'.
+error-example.ts(8,5): error TS2345: Argument of type 'string' is not assignable to parameter of type 'number'.
+```