Early returns over nested conditionals
Named functions over arrows (except callbacks/one-liners)
Strict equality: ===, !== only
const for non-mutated variables
async/await over .then()
Never use any — find specific types
import type for type-only imports
Always use curly braces for if
Never barrel exports in index.ts (harms tree-shaking)
Never write code in index.ts(x) — use specific names
satisfies never in switch default for exhaustiveness
satisfies <Type> over type casting for traceability

Examples

// ✓ Early return
function process(data: Data | null) {
  if (!data) {
    return;
  }
  // process
}

// ✗ Nested
function process(data: Data | null) {
  if (data) {
    // process
  }
}

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

// ✓ One-liner arrow acceptable
const add = (a: number, b: number): number => a + b;

// ✗ Multi-line arrow
const add = (a: number, b: number): number => {
  return a + b;
};

// ✓ Type imports
import type { MyType } from './types';
import { type ReactNode } from 'react';

// ✓ Exhaustiveness + satisfies
function factory(target: 'a' | 'b'): A | B | null {
  switch (target) {
    case 'a':
      return new A();
    case 'b':
      return new B();
    default:
      target satisfies never;
      return null;
  }
}

// ✓ satisfies for traceability
const obj = { key: 'value' } satisfies Record<string, string>;

// ✗ Type casting loses inference
const obj: Record<string, string> = { key: 'value' };

// ✓ Always curly braces
if (!condition) {
  return;
}

// ✗ No braces
if (!condition) return;

typescript-and-javascript

TypeScript/JavaScript Protocol

Type Checking

Code Block Types

Style Rules