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Ultracite Code Standards

This project uses Ultracite, a zero-config preset that enforces strict code quality standards through automated formatting and linting.

Quick Reference

  • Format code: npm exec -- ultracite fix
  • Check for issues: npm exec -- ultracite check
  • Diagnose setup: npm exec -- ultracite doctor

Biome (the underlying engine) provides robust linting and formatting. Most issues are automatically fixable.

Core Principles

Write code that is accessible, performant, type-safe, and maintainable. Focus on clarity and explicit intent over brevity.

Type Safety & Explicitness

  • Use explicit types for function parameters and return values when they enhance clarity
  • Prefer unknown over any when the type is genuinely unknown
  • Use const assertions (as const) for immutable values and literal types
  • Leverage TypeScript's type narrowing instead of type assertions
  • Use meaningful variable names instead of magic numbers - extract constants with descriptive names

Modern JavaScript/TypeScript

  • Use arrow functions for callbacks and short functions
  • Prefer for...of loops over .forEach() and indexed for loops
  • Use optional chaining (?.) and nullish coalescing (??) for safer property access
  • Prefer template literals over string concatenation
  • Use destructuring for object and array assignments
  • Use const by default, let only when reassignment is needed, never var

Async & Promises

  • Always await promises in async functions - don't forget to use the return value
  • Use async/await syntax instead of promise chains for better readability
  • Handle errors appropriately in async code with try-catch blocks
  • Don't use async functions as Promise executors

React & JSX

  • Use function components over class components
  • Call hooks at the top level only, never conditionally
  • Specify all dependencies in hook dependency arrays correctly
  • Use the key prop for elements in iterables (prefer unique IDs over array indices)
  • Nest children between opening and closing tags instead of passing as props
  • Don't define components inside other components
  • Use semantic HTML and ARIA attributes for accessibility:
    • Provide meaningful alt text for images
    • Use proper heading hierarchy
    • Add labels for form inputs
    • Include keyboard event handlers alongside mouse events
    • Use semantic elements (<button>, <nav>, etc.) instead of divs with roles

Error Handling & Debugging

  • Remove console.log, debugger, and alert statements from production code
  • Throw Error objects with descriptive messages, not strings or other values
  • Use try-catch blocks meaningfully - don't catch errors just to rethrow them
  • Prefer early returns over nested conditionals for error cases

Code Organization

  • Keep functions focused and under reasonable cognitive complexity limits
  • Extract complex conditions into well-named boolean variables
  • Use early returns to reduce nesting
  • Prefer simple conditionals over nested ternary operators
  • Group related code together and separate concerns

Security

  • Add rel="noopener" when using target="_blank" on links
  • Avoid dangerouslySetInnerHTML unless absolutely necessary
  • Don't use eval() or assign directly to document.cookie
  • Validate and sanitize user input

Performance

  • Avoid spread syntax in accumulators within loops
  • Use top-level regex literals instead of creating them in loops
  • Prefer specific imports over namespace imports
  • Avoid barrel files (index files that re-export everything)
  • Use proper image components (e.g., Next.js <Image>) over <img> tags

Framework-Specific Guidance

Next.js:

  • Use Next.js <Image> component for images
  • Use next/head or App Router metadata API for head elements
  • Use Server Components for async data fetching instead of async Client Components

React 19+:

  • Use ref as a prop instead of React.forwardRef

Solid/Svelte/Vue/Qwik:

  • Use class and for attributes (not className or htmlFor)

CSS is BEM. This is not optional.

Every class in lib/studio.css is block, block__element, block--modifier, or block__element--modifier. Nothing else.

/* yes */                      /* no */
.projcard { }                  .projcard { }
.projcard__name { }            .nm { }
.projcard--new { }             .projnew { }
                               .projcard .nm { }   /* element through parent */

Never style an element through its parent. .card .path looks harmless and is the shape that makes specificity fights inevitable — the day something else needs a .path, one of the two silently wins. Give the element its block's name and style it directly.

Never invent a bare generic name. .body, .meta, .kind, .row, .status read as global blocks and are really parts of one. Two panels both wanting a "body" is how a rule written for one restyles the other.

npm run check enforces this — lib/bem-check.mjs fails on any class that is not a declared block or namespaced to one. Adding a genuinely new block is a deliberate act: name it in BLOCKS in that file, and say why in the commit.

The ledger

LEGACY in that file lists classes that predate the rule. It exists so the check can fail on anything new without a hundred-name rename landing in one commit.

It only ever shrinks. Converting a class means moving every use of it — studio.css, studio.js, studio.html, and the assertions in verify.mjs that match on class names — then deleting it from LEGACY. The check fails if a name on the ledger is no longer in the CSS, so the list cannot rot into a record of things that no longer exist.

Do not add to it. A new class has no reason to be there.

Testing

  • Write assertions inside it() or test() blocks
  • Avoid done callbacks in async tests - use async/await instead
  • Don't use .only or .skip in committed code
  • Keep test suites reasonably flat - avoid excessive describe nesting

When Biome Can't Help

Biome's linter will catch most issues automatically. Focus your attention on:

  1. Business logic correctness - Biome can't validate your algorithms
  2. Meaningful naming - Use descriptive names for functions, variables, and types
  3. Architecture decisions - Component structure, data flow, and API design
  4. Edge cases - Handle boundary conditions and error states
  5. User experience - Accessibility, performance, and usability considerations
  6. Documentation - Add comments for complex logic, but prefer self-documenting code

Most formatting and common issues are automatically fixed by Biome. Run npm exec -- ultracite fix before committing to ensure compliance.