conductor/code_styleguides/javascript.md

Google JavaScript Style Guide Summary

This document summarizes key rules and best practices from the Google JavaScript Style Guide.

1. Source File Basics

• File Naming: All lowercase, with underscores (_) or dashes (-). Extension must be .js.
• File Encoding: UTF-8.
• Whitespace: Use only ASCII horizontal spaces (0x20). Tabs are forbidden for indentation.

2. Source File Structure

• New files should be ES modules (import/export).
• Exports: Use named exports (export {MyClass};). Do not use default exports.
• Imports: Do not use line-wrapped imports. The .js extension in import paths is mandatory.

3. Formatting

• Braces: Required for all control structures (if, for, while, etc.), even single-line blocks. Use K&R style ("Egyptian brackets").
• Indentation: +2 spaces for each new block.
• Semicolons: Every statement must be terminated with a semicolon.
• Column Limit: 80 characters.
• Line-wrapping: Indent continuation lines at least +4 spaces.
• Whitespace: Use single blank lines between methods. No trailing whitespace.

4. Language Features

• Variable Declarations: Use const by default, let if reassignment is needed. var is forbidden.
• Array Literals: Use trailing commas. Do not use the Array constructor.
• Object Literals: Use trailing commas and shorthand properties. Do not use the Object constructor.
• Classes: Do not use JavaScript getter/setter properties (get name()). Provide ordinary methods instead.
• Functions: Prefer arrow functions for nested functions to preserve this context.
• String Literals: Use single quotes ('). Use template literals (`) for multi-line strings or complex interpolation.
• Control Structures: Prefer for-of loops. for-in loops should only be used on dict-style objects.
• this: Only use this in class constructors, methods, or in arrow functions defined within them.
• Equality Checks: Always use identity operators (=== / !==).

5. Disallowed Features

• with keyword.
• eval() or Function(...string).
• Automatic Semicolon Insertion.
• Modifying builtin objects (Array.prototype.foo = ...).

6. Naming

• Classes: UpperCamelCase.
• Methods & Functions: lowerCamelCase.
• Constants: CONSTANT_CASE (all uppercase with underscores).
• Non-constant Fields & Variables: lowerCamelCase.

7. JSDoc

• JSDoc is used on all classes, fields, and methods.
• Use @param, @return, @override, @deprecated.
• Type annotations are enclosed in braces (e.g., /** @param {string} userName */).

Source: Google JavaScript Style Guide