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