google-ts-styleguide

name

google-ts-styleguide

description

Google TypeScript Style Guide reference for writing, reviewing, and refactoring TypeScript code. Use this skill whenever you are writing TypeScript code, reviewing TypeScript code, refactoring TypeScript, configuring ESLint or linter rules for TypeScript, or when the user asks about TypeScript coding conventions, naming conventions, type system best practices, or import/export patterns. Also trigger when the user mentions 'Google style', 'gts', 'TypeScript style guide', or asks 'how should I name this', 'should I use interface or type', 'how to handle null/undefined' in a TypeScript context. TypeScriptを書く・レビューする・リファクタリングする、ESLintの設定をする、「命名規則」「型の使い方」「import/exportのルール」「interfaceとtypeどっち」「anyを使っていい？」「nullチェックどうする」「Google式」「コーディング規約」「スタイルガイド」などの質問にも対応します。TypeScriptのコードに関する質問や作業であれば積極的にこのスキルを使ってください。

Google TypeScript Style Guide Reference

Google TypeScript Style Guide に基づくコーディングリファレンスです。TypeScriptの実装・コードレビュー・リファクタリング・ESLint設定時に、Googleのコーディング規約に準拠するために使います。

How to use this reference

This guide is organized into topic-specific reference files. Read the relevant file based on the current task:

Topic	File	When to read
File structure & imports/exports	references/source-file-structure.md	Organizing files, import/export patterns, module structure
Language features	references/language-features.md	Variables, arrays, objects, classes, functions, control flow, decorators
Naming conventions	references/naming.md	Naming variables, classes, constants, type parameters, files
Type system	references/type-system.md	Type inference, null/undefined, any/unknown, interfaces vs types, generics
Comments & toolchain	references/comments-and-toolchain.md	JSDoc, comments, @ts-ignore rules, conformance

Quick Reference: Most Common Rules

These are the rules that come up most frequently. For details, read the corresponding reference file.

Naming (see references/naming.md)

• Classes/Interfaces/Types/Enums: UpperCamelCase
• Variables/functions/methods/properties: lowerCamelCase
• Global constants & enum values: CONSTANT_CASE
• Treat acronyms as words: loadHttpUrl, not loadHTTPURL
• No IMyInterface prefix for interfaces
• No trailing/leading underscores for private members

Imports & Exports (see references/source-file-structure.md)

• Use ES6 module syntax only (import/export), never require
• Use named exports exclusively; avoid default exports
• Use import type for type-only imports
• Do not use namespace; use modules
• No mutable exports (export let is prohibited)

Variables & Types (see references/language-features.md, references/type-system.md)

• Use const by default, let when reassignment needed; never var
• Use unknown over any; avoid any wherever possible
• Prefer interface over type literal aliases
• Simple arrays: T[]; complex element types: Array<{...}>
• Prefer optional (field?) over | undefined

Functions & Classes (see references/language-features.md)

• Prefer function declarations for named functions
• Use arrow functions for callbacks, not function expressions
• Mark never-reassigned properties as readonly
• Use parameter properties in constructors
• No #private fields; use TypeScript's private keyword

Control Flow (see references/language-features.md)

• Always use ===/!== (exception: == null for null/undefined check)
• Always use braces for control statements
• Only throw Error instances
• All switch must have default case
• Explicitly end statements with semicolons (no ASI reliance)

ESLint/Linter Configuration Guide

When configuring ESLint or other linters for Google TypeScript style compliance, enforce these core rules:

Must enable:

• @typescript-eslint/no-explicit-any - Discourage any usage
• @typescript-eslint/explicit-module-boundary-types - Encourage explicit return types at module boundaries
• @typescript-eslint/no-non-null-assertion - Discourage ! assertions
• eqeqeq with smart option - Enforce ===/!== with == null exception
• no-var - Forbid var
• prefer-const - Prefer const over let when no reassignment
• curly - Require braces for all control statements
• @typescript-eslint/no-namespace - Forbid namespace
• no-eval - Forbid eval()
• no-debugger - Forbid debugger
• @typescript-eslint/no-wrapper-object-types - Forbid String, Boolean, Number wrapper types
• @typescript-eslint/consistent-type-imports - Enforce import type for type-only imports
• no-restricted-syntax for WithStatement - Forbid with

Naming convention rules (@typescript-eslint/naming-convention):

• UpperCamelCase for classes, interfaces, type aliases, enums, decorators
• lowerCamelCase for variables, functions, methods, parameters, properties
• CONSTANT_CASE for global constants and enum members
• No leading/trailing underscores

Import/export rules:

• no-restricted-exports or plugin rules to forbid default exports
• @typescript-eslint/no-require-imports - Forbid require()

Additional recommended:

• @typescript-eslint/prefer-for-of - Prefer for...of
• @typescript-eslint/no-unnecessary-type-assertion - Remove unnecessary assertions
• @typescript-eslint/prefer-optional-chain - Prefer optional chaining
• @typescript-eslint/prefer-readonly - Prefer readonly for never-reassigned members