TypeScript over JavaScript

Severity: Recommended

Check automatically:

1. Look for TypeScript configuration:

   ls -la tsconfig.json tsconfig.*.json 2>/dev/null
   

2. Count file extensions:

   # TypeScript files
   find . -type f \( -name "*.ts" -o -name "*.tsx" \) -not -path "./node_modules/*" -not -path "./dist/*" | wc -l
   
   # JavaScript files (excluding config files)
   find . -type f \( -name "*.js" -o -name "*.jsx" \) -not -path "./node_modules/*" -not -path "./dist/*" -not -name "*.config.js" -not -name "*.config.mjs" | wc -l
   

3. Check for partial migration (both TS and JS source files):

   # List JS files in src/ that aren't configs
   find ./src -type f \( -name "*.js" -o -name "*.jsx" \) 2>/dev/null
   

4. Check tsconfig strictness:

   cat tsconfig.json | jq '{strict: .compilerOptions.strict, noImplicitAny: .compilerOptions.noImplicitAny, strictNullChecks: .compilerOptions.strictNullChecks}' 2>/dev/null
   

Note: This applies to Node.js/frontend projects. Skip for Python, Go, etc.

Pass criteria:

• Project uses TypeScript (tsconfig.json exists)
• Source files are predominantly .ts/.tsx
• Strict mode enabled ("strict": true) or key strict flags set

Fail criteria:

• Pure JavaScript project with no TypeScript
• TypeScript configured but strict: false and no strict flags
• Mixed codebase with significant JS files in src/ (partial migration stalled)

If JavaScript project, ask user: "Project uses JavaScript instead of TypeScript. Is there a plan to migrate, or a reason TypeScript isn't suitable here?"

If partial migration, ask user: "Found [X] JavaScript files alongside TypeScript. Is migration in progress? What's the timeline?"

Evidence to capture:

• tsconfig.json exists (yes/no)
• File count: .ts/.tsx vs .js/.jsx
• Strict mode status
• Any JS files in src/ that should be migrated

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