tiny-invariant

In practice, tiny-invariant serves as a clean replacement for writing repetitive if-throw blocks. The API is dead simple: invariant(condition, message) throws when the condition is false. What I appreciate most is its production-mode behavior—it strips the message in minified builds while preserving the throw, keeping bundle size minimal without losing stack traces.

From a security perspective, this is mostly safe territory. The library doesn't do anything fancy with user input—it just evaluates your condition and throws. However, you need to be careful about what you pass as the message parameter. If you're interpolating user data into error messages, you're responsible for sanitization. The library won't expose secrets on its own, but sloppy message construction can leak internal state or PII in error logs.

Dependency-wise, it's refreshingly minimal with zero runtime dependencies, reducing supply chain attack surface. The codebase is tiny enough to audit in minutes. My only real concern is that it doesn't provide type narrowing in TypeScript as effectively as assertion functions (asserts keyword), so you may need to pair it with type guards for proper type safety.

In production, tiny-invariant is exactly what it claims to be: a lightweight assertion helper that throws when conditions fail. The entire implementation is under 10 lines, which means zero surprises in behavior or performance. I've used it extensively in React components and API handlers where you need to validate assumptions without adding bloat.

The library strips messages in production builds when used with proper bundlers (Webpack, Rollup, etc.), which is critical for keeping bundle sizes down. Error messages are clear and include the failed condition in dev mode, making debugging straightforward. The API is dead simple: `invariant(condition, message)` - if false, it throws. No configuration needed, no initialization, no memory footprint to speak of.

One gotcha: it throws Error objects, not custom types, so you can't easily distinguish invariant failures from other errors in your error handling middleware without parsing message strings. Also, there's no built-in support for formatted messages with interpolation - you need template literals for that. For most use cases though, this simplicity is exactly what you want when you just need assertions without the weight of a full validation library.

In practice, tiny-invariant is exactly what it says: a minimal function that throws when conditions fail. The API is dead simple - `invariant(condition, message)` - and it behaves predictably across codebases. What makes it security-relevant is its production mode behavior: message strings are stripped in production builds (when NODE_ENV === 'production'), preventing sensitive internal state from leaking through error messages to end users.

The library has zero dependencies, which is a significant win for supply chain risk. It's a single file doing one thing, making it easy to audit. The source is straightforward TypeScript with no complex logic paths. However, the message-stripping behavior requires bundler cooperation and proper NODE_ENV configuration - if your build pipeline doesn't set this correctly, you'll ship full error messages to production.

For type safety, it includes TypeScript assertion signatures that properly narrow types after the invariant check, which prevents common validation bugs. The predictable throwing behavior (always Error instances) makes error handling straightforward in try-catch blocks.