TypeScript Code Checker: Free Online Security and Type-Safety Analysis

CodeSlick analyzes TypeScript code with 64 security checks covering the full OWASP Top 10:2025 attack surface for TypeScript applications. Unlike generic linters, CodeSlick understands TypeScript-specific patterns: the TypeScript Compiler API provides 95%+ type error detection, catching type-unsafe patterns that escape static analysis in other tools.

The analysis runs in under 3 seconds with zero configuration — paste code or upload a file, and results include CWE classification, CVSS severity scoring, and AI-powered fix suggestions specific to TypeScript idioms.

CodeSlick covers 64 TypeScript-specific security checks organized by vulnerability class:

Injection (A03)

• SQL injection: Template literals and string concatenation in database queries, including TypeORM raw queries and Prisma queryRaw
• XSS: innerHTML, dangerouslySetInnerHTML, document.write() with dynamic content
• Command injection: exec(), execSync(), spawn() with user-controlled arguments
• Path traversal: readFile(), createReadStream() with unsanitized path parameters

Authentication & Cryptography

• JWT vulnerabilities: Missing algorithm validation, weak secrets, missing expiration checks
• Hardcoded secrets: 38 patterns covering API keys, tokens, and private keys in TypeScript source
• Weak cryptography: MD5, SHA-1 usage; ECB mode; Math.random() in security-sensitive contexts
• Insecure cookies: Missing httpOnly, secure, and sameSite attributes

TypeScript-Specific Checks

• Type assertion bypasses: as any and as unknown as T patterns that defeat TypeScript safety in security-sensitive code
• Prototype pollution: Unsafe dynamic property assignment with user-controlled keys
• Non-null assertion abuse: ! operator on user-supplied values passed to sensitive operations

CodeSlick integrates directly with the TypeScript Compiler API — the same engine that powers VS Code's IntelliSense — to provide analysis unavailable in other static analysis tools.

The Compiler API enables:

• Type-flow analysis: Tracking how values propagate through generic types, conditional types, and mapped types to find type-unsafe code paths
• 95%+ type error detection: Identifying likely runtime type errors from static analysis of TypeScript's type narrowing logic
• Framework-aware analysis: Understanding Express.js Request types, Next.js GetServerSideProps return types, and React component prop types to detect type boundary violations

This integration is unique to CodeSlick among SAST tools. Most scanners treat TypeScript as "JavaScript with type annotations" and miss type-level security issues entirely.

CodeSlick includes 17 TypeScript-specific AI code detection patterns that identify code likely generated by GitHub Copilot, ChatGPT, Claude, and Cursor. AI-generated TypeScript tends toward specific hallucination patterns:

• Non-existent method calls: Methods that do not exist on TypeScript standard library types
• Incorrect generic constraints: Overly broad generic type parameters that mask runtime errors
• LLM fingerprints: Patterns characteristic of specific LLMs — Copilot's TODO comments, Claude's verbose interface definitions, ChatGPT's over-qualified type assertions

AI detection findings are separate from security findings and do not block CI/CD by default — they flag code that needs human review before merge.

CodeSlick's TypeScript checker requires no account, no setup, and no configuration:

1. Visit codeslick.dev/analyze
2. Select TypeScript from the language selector
3. Paste your TypeScript code or upload a .ts or .tsx file
4. Click Analyze
5. Review findings in the two-tier display: Tier 1 (syntax errors with red highlights) and Tier 2 (security findings with CVSS scores)
6. Click any finding to see the AI-generated fix suggestion

Results appear in under 3 seconds. For team-wide analysis on every pull request, install the CodeSlick GitHub App.