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

module-

lang-

type-

naming-

control-

func-

data-

format-

Quick Reference

1. Module System & Imports (CRITICAL)

• module-avoid-circular-dependencies

  - Prevent loading failures from circular imports

• module-file-extension-in-imports

  - Include .js extension in import paths

• module-named-exports-over-default

  - Prefer named exports for consistency

• module-no-duplicate-imports

  - Import from same file only once

• module-no-import-aliasing

  - Keep original export names

• module-source-file-structure

  - Follow standard file structure order

2. Language Features (CRITICAL)

• lang-const-over-let-over-var

  - Use const by default, never var

• lang-es6-classes-over-prototypes

  - Use class syntax over prototype manipulation

• lang-explicit-semicolons

  - Always use explicit semicolons

• lang-no-eval

  - Never use eval or Function constructor

• lang-no-modify-builtins

  - Never modify built-in prototypes

• lang-no-non-standard-features

  - Use only standard ECMAScript features

• lang-no-primitive-wrappers

  - Never use primitive wrapper objects

• lang-no-with-statement

  - Never use the with statement

3. Type Safety & JSDoc (HIGH)

• type-cast-with-parentheses

  - Use parentheses for type casts

• type-enum-annotations

  - Annotate enums with static literal values

• type-explicit-nullability

  - Use explicit nullability modifiers

• type-jsdoc-required-for-exports

  - Require JSDoc for exported functions

• type-template-parameters

  - Always specify template parameters

• type-typedef-for-complex-types

  - Use typedef for complex object types

4. Naming Conventions (HIGH)

• naming-constant-case-for-constants

  - Use CONSTANT_CASE for immutable values

• naming-descriptive-over-brief

  - Prefer descriptive names over brevity

• naming-file-naming-conventions

  - Use lowercase with dashes or underscores

• naming-lowercamelcase-for-methods

  - Use lowerCamelCase for methods and variables

• naming-no-dollar-prefix

  - Avoid dollar sign prefix in identifiers

• naming-uppercamelcase-for-classes

  - Use UpperCamelCase for classes

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

• control-comment-empty-catch

  - Document empty catch blocks

• control-for-of-over-for-in

  - Prefer for-of over for-in

• control-strict-equality

  - Use strict equality except for null checks

• control-switch-default-last

  - Always include default case in switch

• control-throw-error-objects

  - Always throw Error objects

6. Functions & Parameters (MEDIUM)

• func-arrow-functions-for-nested

  - Prefer arrow functions for nested functions

• func-arrow-parentheses

  - Always use parentheses around arrow params

• func-default-parameters

  - Use default parameters instead of conditionals

• func-rest-parameters-over-arguments

  - Use rest parameters over arguments

• func-spread-over-apply

  - Use spread operator instead of apply

7. Objects & Arrays (MEDIUM)

• data-array-literals-over-constructor

  - Use array literals over Array constructor

• data-destructuring-for-multiple-values

  - Use destructuring for multiple properties

• data-no-mixing-quoted-unquoted-keys

  - Never mix quoted and unquoted keys

• data-object-literals-over-constructor

  - Use object literals over constructor

• data-spread-over-concat-slice

  - Use spread over concat and slice

• data-trailing-commas

  - Use trailing commas in multi-line literals

8. Formatting & Style (LOW)

• format-braces-required

  - Always use braces for control structures

• format-column-limit

  - Limit lines to 80 characters

• format-one-statement-per-line

  - Place one statement per line

• format-single-quotes

  - Use single quotes for string literals

• format-two-space-indent

  - Use two-space indentation

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Full Compiled Document

For a complete compiled guide with all rules, see AGENTS.md.

Reference Files