1. Basic Characteristics
2. Medium Characteristics
3. Advanced Characteristics
4. Expert Characteristics
5. Conclusion

1. Static Typing: Unlike JavaScript, TypeScript enforces type safety, preventing runtime type-related errors.
2. Type Annotations: Developers can explicitly define variable and function return types.
3. Compilation to JavaScript: TypeScript is transpiled to JavaScript using tsc (TypeScript Compiler).
4. ES6+ Features Support: Supports modern JavaScript syntax and compiles it down to ES5 if needed.
5. Basic Type System:
   • number, string, boolean, null, undefined, any, void
   • Arrays: number[], Array<string>
   • Tuples: [string, number]
   • Enums: enum Colors { Red, Green, Blue }
6. Function Typing:

   function add(a: number, b: number): number {
       return a + b;
   }

7. Interfaces: Contracts for object shapes.

   interface User {
       id: number;
       name: string;
   }

1. Union and Intersection Types:

   type ID = string | number;
   type Employee = { id: number } & { name: string };

2. Optional and Readonly Properties:

   interface Config {
       readonly apiKey: string;
       timeout?: number;
   }

3. Generics:

   function identity<T>(arg: T): T {
       return arg;
   }

4. Type Inference: TypeScript can infer types without explicit annotations.
5. Enums with Custom Values:

   enum StatusCode {
       Success = 200,
       NotFound = 404,
   }

6. Type Guards:

   function isNumber(value: any): value is number {
       return typeof value === 'number';
   }

1. Mapped Types:

   type Readonly<T> = { readonly [K in keyof T]: T[K] };

2. Conditional Types:

   type IsString<T> = T extends string ? true : false;

3. Discriminated Unions (for better type narrowing):

   interface Circle {
       kind: "circle";
       radius: number;
   }
   interface Square {
       kind: "square";
       side: number;
   }
   type Shape = Circle | Square;
   function getArea(shape: Shape) {
       if (shape.kind === "circle") {
           return Math.PI * shape.radius ** 2;
       }
   }

4. Decorators (Experimental Feature in Angular and NestJS):

   function Log(target: any, key: string) {
       console.log(`Calling method ${key}`);
   }
   class Example {
       @Log
       greet() {
           console.log("Hello");
       }
   }

5. Utility Types (Partial, Required, Readonly, Pick, Omit)

   type PartialUser = Partial<{ id: number; name: string }>

6. Namespace and Module Resolution for Large-Scale Projects

1. Abstract Classes and Advanced Object-Oriented Features

   abstract class Animal {
       abstract makeSound(): void;
   }

2. Deep Type Inference with Conditional Types

   type InferType<T> = T extends { type: infer U } ? U : never;

3. Deeply Nested Type Checking and Recursive Types

   type JSONValue = string | number | boolean | { [x: string]: JSONValue };

4. Module Federation in Large Applications (Micro Frontends with Angular/Nx)
5. TypeScript Compiler Internals (TSConfig, Custom Transformers)
   • strict: Enables strict type checking
   • moduleResolution: Determines how modules are resolved
6. Performance Optimizations with tsc and Babel
7. Type-Driven Development (TDD with TypeScript in Enterprise)
8. Applying TypeScript in Full-Stack Development (Angular, NestJS, Deno)

TypeScript provides a strong foundation for scalable JavaScript applications. By mastering the expert-level features, developers can enhance maintainability, performance, and architecture for enterprise-level software solutions.