Typescript Best Practices

Type Safety & Static Analysis

1. Use Interfaces to Define Object Shapes
   Leverage interfaces to define the structure of objects and ensure that they include the necessary properties and methods. This provides type safety and clear expectations of object structure, helping to catch errors early in development.

   typescript
   interface User {
       name: string;
       age: number;
       isActive: boolean;
   }
   

2. Apply Type Annotations for Clarity
   Use type annotations to specify the types of variables, function parameters, and return values. Type annotations help prevent type errors at compile time and make the code easier to understand.

   typescript
   function greet(user: User): string {
       return `Hello, ${user.name}!`;
   }
   

3. Enable Strict Compiler Options
   Enable the strict compiler option to activate a higher level of type checking. This enforces stricter rules for type inference, helping to catch potential issues and ensuring your code is more robust.

   json
   "compilerOptions": {
     "strict": true
   }
   

4. Require Explicit Type Annotations with noImplicitAny
   Use the noImplicitAny option to require explicit type annotations. This prevents variables from defaulting to any type, which could lead to unintended behavior or runtime errors.

   json
   "compilerOptions": {
     "noImplicitAny": true
   }
   

5. Remove Unused Code with noUnusedLocals and noUnusedParameters
   Enforce cleaner code by enabling noUnusedLocals and noUnusedParameters to detect and remove unused variables and parameters. This improves code readability and maintainability.

   json
   "compilerOptions": {
     "noUnusedLocals": true,
     "noUnusedParameters": true
   }
   

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Code Structure & Reusability

6. Utilize Classes and Inheritance for Behavior Encapsulation
   Classes provide a way to define types and encapsulate behavior. Use inheritance to extend functionality, making your code more modular, reusable, and easier to maintain.

   typescript
   class Person {
       constructor(public name: string, public age: number) {}
   }
   
   class Employee extends Person {
       constructor(name: string, age: number, public department: string) {
           super(name, age);
       }
   }
   

7. Use Enums for Named Constants
   Enums allow you to define a set of named constants, providing more meaningful values in your code and reducing errors from using raw values. They are particularly useful for representing fixed sets of values, like status codes or days of the week.

   typescript
   enum Status {
       Active = "ACTIVE",
       Inactive = "INACTIVE",
       Pending = "PENDING"
   }
   

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Advanced Type Handling

8. Implement Type Guards for Runtime Type Checking
   Type guards allow you to narrow down types at runtime, making it easy to handle different types within a single function. This is useful when working with unions or unknown types.

   typescript
   function isString(value: any): value is string {
       return typeof value === 'string';
   }
   
   function printValue(value: string | number) {
       if (isString(value)) {
           console.log(value.toUpperCase());
       } else {
           console.log(value.toFixed(2));
       }
   }
   

9. Leverage Decorators for Metadata and Functionality
   Decorators enable you to add metadata or additional behavior to classes and properties. They allow for more declarative, reusable functionality, particularly useful in frameworks like Angular.

   typescript
   function log(target: any, key: string) {
       console.log(`Property ${key} accessed`);
   }
   
   class MyClass {
       @log
       myProperty: string = "Hello";
   }
   

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Coding Standards & Tools

10. Enforce Consistent Code Style with TSLint and Prettier
    Use TSLint (or its successor ESLint with TypeScript support) to enforce consistent coding conventions, and Prettier to automatically format your code. These tools ensure uniform code style and help avoid trivial formatting disputes among team members.

• TSLint: Helps catch potential issues and enforces best practices.
• Prettier: Automatically formats your code to follow a consistent style.

Example configuration for TSLint:

json
{
    "extends": ["tslint:recommended"],
    "rules": {
        "no-console": false
    }
}

Example configuration for Prettier:

json
{
    "singleQuote": true,
    "trailingComma": "all"
}

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Conclusion

By following these best practices, you can ensure that your TypeScript code is type-safe, efficient, and maintainable. Proper use of interfaces, type annotations, and compiler options will catch errors early, while classes, enums, and decorators enable you to write reusable and extensible code. Additionally, enforcing coding standards with tools like TSLint and Prettier will help maintain consistency across your projects.