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](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