Typescript Code Review And Linting

TypeScript Code Review and Linting Skill

Metadata (Tier 1)

Keywords: eslint, typescript, type checking, refactor, ts review

File Patterns: *.ts, *.tsx, *.js, *.jsx

Modes: code_review

Instructions (Tier 2)

ESLint Configuration

// eslint.config.js
import tseslint from '@typescript-eslint/eslint-plugin';

export default [
  {
    plugins: { '@typescript-eslint': tseslint },
    rules: {
      '@typescript-eslint/no-explicit-any': 'error',
      '@typescript-eslint/no-unused-vars': 'error',
      'no-console': 'warn',
    }
  }
];

Critical Type Safety Rules

@typescript-eslint/no-explicit-any

// ❌ Defeats TypeScript
function process(data: any): any {
    return data.value;
}

// ✅ Use proper types
interface Data {
    value: string;
}
function process(data: Data): string {
    return data.value;
}

@typescript-eslint/no-unsafe-assignment

// ❌ Unsafe
const value: string = getData();  // getData returns 'any'

// ✅ Type assertion or guard
const value = getData() as string;
// Or
if (typeof getData() === 'string') {
    const value: string = getData();
}

React-Specific Rules

react/no-array-index-key

// ❌ Causes rendering bugs
{items.map((item, index) => (
    <div key={index}>{item.name}</div>
))}

// ✅ Use unique ID
{items.map(item => (
    <div key={item.id}>{item.name}</div>
))}

react/no-danger

// ❌ XSS risk
<div dangerouslySetInnerHTML={{__html: userInput}} />

// ✅ Sanitize or use markdown
import DOMPurify from 'dompurify';
<div dangerouslySetInnerHTML={{__html: DOMPurify.sanitize(userInput)}} />

TypeScript Compiler Errors

// TS2339: Property 'name' does not exist on type '{}'
const user = {};
console.log(user.name);  // ❌

// ✅ Fix: Define interface
interface User {
    name: string;
}
const user: User = { name: "Alice" };

Anti-Patterns

❌ Overuse of any type ❌ Type assertions without validation ❌ Ignoring compiler errors with @ts-ignore ❌ Not enabling strict mode