# JS Google

> Google JavaScript Best Practices

- Skill: `comeonoliver/js-google` (Agent Skill)
- Install (CLI): `npx skillmds@latest add comeonoliver/js-google`
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- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: ComeOnOliver (https://skillmd.com/u/comeonoliver)
- Updated: 2026-09-21
- Page: https://skillmd.com/skills/comeonoliver/js-google

---

# Google JavaScript Best Practices

Comprehensive JavaScript style and best practices guide based on Google's official JavaScript Style Guide, designed for AI agents and LLMs. Contains 47 rules across 8 categories, prioritized by impact to guide automated refactoring and code generation.

## When to Apply

Reference these guidelines when:
- Writing new JavaScript or ES6+ code
- Structuring modules and managing imports/exports
- Adding JSDoc type annotations and documentation
- Reviewing code for naming and style consistency
- Refactoring existing JavaScript code

## Rule Categories by Priority

| Priority | Category | Impact | Prefix |
|----------|----------|--------|--------|
| 1 | Module System & Imports | CRITICAL | `module-` |
| 2 | Language Features | CRITICAL | `lang-` |
| 3 | Type Safety & JSDoc | HIGH | `type-` |
| 4 | Naming Conventions | HIGH | `naming-` |
| 5 | Control Flow & Error Handling | MEDIUM-HIGH | `control-` |
| 6 | Functions & Parameters | MEDIUM | `func-` |
| 7 | Objects & Arrays | MEDIUM | `data-` |
| 8 | Formatting & Style | LOW | `format-` |

## Quick Reference

### 1. Module System & Imports (CRITICAL)

- [`module-avoid-circular-dependencies`](references/module-avoid-circular-dependencies.md) - Prevent loading failures from circular imports
- [`module-file-extension-in-imports`](references/module-file-extension-in-imports.md) - Include .js extension in import paths
- [`module-named-exports-over-default`](references/module-named-exports-over-default.md) - Prefer named exports for consistency
- [`module-no-duplicate-imports`](references/module-no-duplicate-imports.md) - Import from same file only once
- [`module-no-import-aliasing`](references/module-no-import-aliasing.md) - Keep original export names
- [`module-source-file-structure`](references/module-source-file-structure.md) - Follow standard file structure order

### 2. Language Features (CRITICAL)

- [`lang-const-over-let-over-var`](references/lang-const-over-let-over-var.md) - Use const by default, never var
- [`lang-es6-classes-over-prototypes`](references/lang-es6-classes-over-prototypes.md) - Use class syntax over prototype manipulation
- [`lang-explicit-semicolons`](references/lang-explicit-semicolons.md) - Always use explicit semicolons
- [`lang-no-eval`](references/lang-no-eval.md) - Never use eval or Function constructor
- [`lang-no-modify-builtins`](references/lang-no-modify-builtins.md) - Never modify built-in prototypes
- [`lang-no-non-standard-features`](references/lang-no-non-standard-features.md) - Use only standard ECMAScript features
- [`lang-no-primitive-wrappers`](references/lang-no-primitive-wrappers.md) - Never use primitive wrapper objects
- [`lang-no-with-statement`](references/lang-no-with-statement.md) - Never use the with statement

### 3. Type Safety & JSDoc (HIGH)

- [`type-cast-with-parentheses`](references/type-cast-with-parentheses.md) - Use parentheses for type casts
- [`type-enum-annotations`](references/type-enum-annotations.md) - Annotate enums with static literal values
- [`type-explicit-nullability`](references/type-explicit-nullability.md) - Use explicit nullability modifiers
- [`type-jsdoc-required-for-exports`](references/type-jsdoc-required-for-exports.md) - Require JSDoc for exported functions
- [`type-template-parameters`](references/type-template-parameters.md) - Always specify template parameters
- [`type-typedef-for-complex-types`](references/type-typedef-for-complex-types.md) - Use typedef for complex object types

### 4. Naming Conventions (HIGH)

- [`naming-constant-case-for-constants`](references/naming-constant-case-for-constants.md) - Use CONSTANT_CASE for immutable values
- [`naming-descriptive-over-brief`](references/naming-descriptive-over-brief.md) - Prefer descriptive names over brevity
- [`naming-file-naming-conventions`](references/naming-file-naming-conventions.md) - Use lowercase with dashes or underscores
- [`naming-lowercamelcase-for-methods`](references/naming-lowercamelcase-for-methods.md) - Use lowerCamelCase for methods and variables
- [`naming-no-dollar-prefix`](references/naming-no-dollar-prefix.md) - Avoid dollar sign prefix in identifiers
- [`naming-uppercamelcase-for-classes`](references/naming-uppercamelcase-for-classes.md) - Use UpperCamelCase for classes

### 5. Control Flow & Error Handling (MEDIUM-HIGH)

- [`control-comment-empty-catch`](references/control-comment-empty-catch.md) - Document empty catch blocks
- [`control-for-of-over-for-in`](references/control-for-of-over-for-in.md) - Prefer for-of over for-in
- [`control-strict-equality`](references/control-strict-equality.md) - Use strict equality except for null checks
- [`control-switch-default-last`](references/control-switch-default-last.md) - Always include default case in switch
- [`control-throw-error-objects`](references/control-throw-error-objects.md) - Always throw Error objects

### 6. Functions & Parameters (MEDIUM)

- [`func-arrow-functions-for-nested`](references/func-arrow-functions-for-nested.md) - Prefer arrow functions for nested functions
- [`func-arrow-parentheses`](references/func-arrow-parentheses.md) - Always use parentheses around arrow params
- [`func-default-parameters`](references/func-default-parameters.md) - Use default parameters instead of conditionals
- [`func-rest-parameters-over-arguments`](references/func-rest-parameters-over-arguments.md) - Use rest parameters over arguments
- [`func-spread-over-apply`](references/func-spread-over-apply.md) - Use spread operator instead of apply

### 7. Objects & Arrays (MEDIUM)

- [`data-array-literals-over-constructor`](references/data-array-literals-over-constructor.md) - Use array literals over Array constructor
- [`data-destructuring-for-multiple-values`](references/data-destructuring-for-multiple-values.md) - Use destructuring for multiple properties
- [`data-no-mixing-quoted-unquoted-keys`](references/data-no-mixing-quoted-unquoted-keys.md) - Never mix quoted and unquoted keys
- [`data-object-literals-over-constructor`](references/data-object-literals-over-constructor.md) - Use object literals over constructor
- [`data-spread-over-concat-slice`](references/data-spread-over-concat-slice.md) - Use spread over concat and slice
- [`data-trailing-commas`](references/data-trailing-commas.md) - Use trailing commas in multi-line literals

### 8. Formatting & Style (LOW)

- [`format-braces-required`](references/format-braces-required.md) - Always use braces for control structures
- [`format-column-limit`](references/format-column-limit.md) - Limit lines to 80 characters
- [`format-one-statement-per-line`](references/format-one-statement-per-line.md) - Place one statement per line
- [`format-single-quotes`](references/format-single-quotes.md) - Use single quotes for string literals
- [`format-two-space-indent`](references/format-two-space-indent.md) - Use two-space indentation

## How to Use

Read individual reference files for detailed explanations and code examples:

- [Section definitions](references/_sections.md) - Category structure and impact levels
- [Rule template](assets/templates/_template.md) - Template for adding new rules

## Full Compiled Document

For a complete compiled guide with all rules, see [AGENTS.md](AGENTS.md).

## Reference Files

| File | Description |
|------|-------------|
| [AGENTS.md](AGENTS.md) | Complete compiled guide with all rules |
| [references/_sections.md](references/_sections.md) | Category definitions and ordering |
| [assets/templates/_template.md](assets/templates/_template.md) | Template for new rules |
| [metadata.json](metadata.json) | Version and reference information |