From fec754a44a07179b0ad204a43399b0b1f702370c Mon Sep 17 00:00:00 2001
From: Martin Ibled <martin.ibled@ekino.com>
Date: Sat, 12 Oct 2024 00:07:41 +0200
Subject: [PATCH] [FEATURE]: add TS checklist

---
 typescript/README.md | 177 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 177 insertions(+)

diff --git a/typescript/README.md b/typescript/README.md
index c542c6b..554d6a6 100644
--- a/typescript/README.md
+++ b/typescript/README.md
@@ -1 +1,178 @@
 # TypeScript Best Practices
+
+1. **Consistent Coding Style**:
+   - **Explanation**: Use a linter like ESLint to maintain a consistent coding style.
+      - @typescript-eslint/parser
+      - @typescript-eslint/eslint-plugin
+      - eslint-config-airbnb-typescript
+
+   Configure ESLint: Create or modify the `.eslintrc.json` file at the root of your project with the following configuration:
+
+   ```json
+    {
+        "extends": [
+            "airbnb-typescript"
+        ],
+        "parser": "@typescript-eslint/parser",
+        "parserOptions": {
+            "project": "./tsconfig.json"
+        },
+        "plugins": [
+            "@typescript-eslint"
+        ],
+        "rules": {
+            "semi": ["error", "always"],
+            "quotes": ["error", "single"],
+            "no-unused-vars": "error",
+            "eqeqeq": ["error", "always"],
+            "curly": ["error", "all"],
+            "no-console": "warn",
+            "consistent-return": "error",
+            "prefer-const": "error"
+        }
+    }
+    ```
+
+   This configuration allows you to benefit from Airbnb's best practices while integrating TypeScript specifics.
+
+2. **Type Annotations**:
+   - **Explanation**: Provide type annotations for function arguments and return values to ensure type safety.
+   ```typescript
+   function greet(name: string): string {
+     return `Hello, ${name}`;
+   }
+   ```
+
+3. **Interfaces**:
+   - **Explanation**: Prefer interfaces over type aliases for defining object shapes.
+   ```typescript
+   interface User {
+     name: string;
+     age: number;
+   }
+   ```
+
+4. **Avoid `any`**:
+   - **Explanation**: Using `any` defeats the purpose of TypeScript's type safety.
+   ```typescript
+   let data: any; // Avoid this
+   let userData: User; // Prefer this
+   ```
+
+5. **Strict Null Checks**:
+   - **Explanation**: Enable strict null checks to prevent null or undefined errors.
+   ```typescript
+   let nullableString: string | null = null;
+   ```
+
+6. **Use `readonly` for Immutability**:
+   - **Explanation**: Use `readonly` for properties that should not be modified after initialization.
+    ```typescript
+    interface User {
+      readonly id: number;
+      name: string;
+      age: number;
+    }
+    ```
+
+7. **Prefer `const` over `let`**:
+   - **Explanation**: Use `const` for variables that will not be reassigned.
+    ```typescript
+    const userName: string = 'Alice';
+    ```
+
+8. **Use Utility Types**:
+   - **Explanation**: Use TypeScript utility types like `Partial`, `Pick`, `Omit` to manipulate types.
+    ```typescript
+    interface User {
+      name: string;
+      age: number;
+      email: string;
+    }
+
+    type UserWithoutEmail = Omit<User, 'email'>;
+    ```
+
+9. **Avoid Magic Numbers and Strings**:
+   - **Explanation**: Define constants for recurring values to make the code more readable and maintainable.
+    ```typescript
+    const MAX_USERS = 100;
+
+    function createUser(name: string): User {
+      if (users.length >= MAX_USERS) {
+        throw new Error('Max users reached');
+      }
+      // ...
+    }
+    ```
+
+10. **Document Your Code**:
+- **Explanation**: Use JSDoc comments to document functions and interfaces.
+  ```typescript
+  /**
+   * Greets a user by name.
+   * @param name - The name of the user.
+   * @returns A greeting message.
+   */
+  function greet(name: string): string {
+    return `Hello, ${name}`;
+  }
+  ```
+
+11. **Use of Enums**:
+- **Explanation**: Use enums to represent a set of named values, improving code readability and maintainability.
+  ```typescript
+  enum UserRole {
+    Admin = 'Admin',
+    User = 'User',
+    Guest = 'Guest'
+  }
+
+   function getPermissions(role: UserRole) {
+    switch (role) {
+     case UserRole.Admin:
+     return ['read', 'write', 'delete'];
+     case UserRole.User:
+     return ['read', 'write'];
+     case UserRole.Guest:
+     return ['read'];
+    }
+   }
+    ```
+
+12. **Use of Literal Types**:
+- **Explanation**: Use literal types for simple sets of values to ensure type safety and flexibility.
+  ```typescript
+  type OrderStatus = 'Pending' | 'Shipped' | 'Delivered' | 'Cancelled';
+
+   function updateOrderStatus(orderId: number, status: OrderStatus) {
+   // Logic to update order status
+   console.log(`Order ${orderId} is now ${status}`);
+   }
+   ```
+
+13. **Use of `const` with `as const`**:
+- **Explanation**: Use `const` with `as const` to define immutable objects, ensuring that values are not accidentally modified.
+  ```typescript
+  const Config = {
+  apiUrl: 'https://api.example.com',
+  timeout: 5000,
+  retryAttempts: 3
+  } as const;
+
+   type ConfigType = typeof Config;
+   
+   function initializeApp(config: ConfigType) {
+   console.log(`Initializing app with API URL: ${config.apiUrl}`);
+   // App initialization logic
+   }
+    ```
+
+
+## Ressources
+
+- [TypeScript GitBook : Un ouvrage open-source sur TypeScript](https://basarat.gitbook.io/typescript/)
+- [Typescriptlang Handbook](https://www.typescriptlang.org/docs/handbook/intro.html)
+- [The Concise TypeScript Book](https://typescript-book.vercel.app/books/the-concise-typescript-book/)
+- [TS Playground](https://www.typescriptlang.org/play)
+- [TS config cheat sheet](https://www.totaltypescript.com/tsconfig-cheat-sheet)