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

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