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

• 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

File Description

AGENTS.md Complete compiled guide with all rules

references/_sections.md Category definitions and ordering

assets/templates/_template.md Template for new rules

metadata.json Version and reference information