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skills/implementing-features/languages/JAVASCRIPT.md

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+# JavaScript/TypeScript Quality Standards
+
+**Load this file when:** Implementing features in JavaScript or TypeScript projects
+
+## Validation Commands
+
+**JavaScript:**
+```bash
+# Linting
+npx eslint . --fix
+
+# Formatting
+npx prettier --write .
+
+# Tests
+npm test
+
+# Full Validation Pipeline
+npx eslint . && npx prettier --check . && npm test
+```
+
+**TypeScript:**
+```bash
+# Linting
+npx eslint . --fix
+
+# Formatting
+npx prettier --write .
+
+# Type Checking
+npx tsc --noEmit
+
+# Tests
+npm test
+
+# Full Validation Pipeline
+npx eslint . && npx prettier --check . && npx tsc --noEmit && npm test
+```
+
+## Required Standards
+
+```yaml
+Code Style:
+  - Line length: 100-120 characters
+  - Semicolons: Consistent (prefer with)
+  - Quotes: Single or double (consistent)
+  - Trailing commas: Always in multiline
+
+Testing:
+  - Framework: Jest, Mocha, or Vitest
+  - Coverage: >= 80%
+  - Test files: *.test.js, *.spec.js
+  - Mocking: Prefer dependency injection
+  - Async: Use async/await, not callbacks
+
+Documentation:
+  - JSDoc for all exported functions
+  - README for packages
+  - Type definitions (TypeScript or JSDoc)
+  - API documentation for libraries
+
+TypeScript Specific:
+  - Strict mode enabled
+  - No 'any' types (use 'unknown' if needed)
+  - Proper interface/type definitions
+  - Generic types where appropriate
+  - Discriminated unions for state
+
+Error Handling:
+  - Try/catch for async operations
+  - Error boundaries (React)
+  - Proper promise handling
+  - No unhandled promise rejections
+```
+
+## Quality Checklist
+
+**Before Declaring Complete:**
+- [ ] No linting errors (`eslint .`)
+- [ ] Code formatted (`prettier --check .`)
+- [ ] Type checking passes (TS: `tsc --noEmit`)
+- [ ] All tests pass (`npm test`)
+- [ ] Test coverage >= 80%
+- [ ] No 'any' types (TypeScript)
+- [ ] All exported functions have JSDoc
+- [ ] Async operations properly handled
+- [ ] Error boundaries implemented (React)
+- [ ] No console.log in production code
+
+## Example Quality Pattern
+
+**TypeScript:**
+```typescript
+/**
+ * Load configuration from YAML file.
+ *
+ * @param configPath - Path to configuration file
+ * @returns Parsed configuration object
+ * @throws {Error} If file doesn't exist or YAML is invalid
+ *
+ * @example
+ * ```ts
+ * const config = await loadConfig('./config.yaml');
+ * console.log(config.apiKey);
+ * ```
+ */
+export async function loadConfig(configPath: string): Promise<Config> {
+  if (!fs.existsSync(configPath)) {
+    throw new Error(`Config not found: ${configPath}`);
+  }
+
+  try {
+    const contents = await fs.promises.readFile(configPath, 'utf-8');
+    const config = yaml.parse(contents) as Config;
+    return config;
+  } catch (error) {
+    throw new Error(`Invalid YAML in ${configPath}: ${error.message}`);
+  }
+}
+```
+
+**JavaScript with JSDoc:**
+```javascript
+/**
+ * @typedef {Object} Config
+ * @property {string} apiKey - API key for service
+ * @property {number} timeout - Request timeout in ms
+ */
+
+/**
+ * Load configuration from YAML file.
+ *
+ * @param {string} configPath - Path to configuration file
+ * @returns {Promise<Config>} Parsed configuration object
+ * @throws {Error} If file doesn't exist or YAML is invalid
+ */
+export async function loadConfig(configPath) {
+  if (!fs.existsSync(configPath)) {
+    throw new Error(`Config not found: ${configPath}`);
+  }
+
+  try {
+    const contents = await fs.promises.readFile(configPath, 'utf-8');
+    const config = yaml.parse(contents);
+    return config;
+  } catch (error) {
+    throw new Error(`Invalid YAML in ${configPath}: ${error.message}`);
+  }
+}
+```
+
+---
+
+*JavaScript/TypeScript-specific quality standards for production-ready code*