is-nan

This is essentially a bulletproof implementation of Number.isNaN that handles the quirks of JavaScript's original global isNaN function. In production, it's completely transparent - zero runtime overhead once loaded, no configuration needed, and it just works. The implementation correctly differentiates between NaN and non-numeric values, unlike the global isNaN which coerces arguments to numbers first.

From an operations perspective, this is the ideal dependency: trivial bundle size (under 1KB), no external dependencies, no configuration surface area to manage, and no runtime state. It either polyfills the native method or uses it directly. There are no connection pools, no retries, no timeouts - it's a pure function that executes in microseconds. The only consideration is whether you actually need it, since all modern Node versions (6+) and browsers have native Number.isNaN support.

The main value is in legacy environments or when you need absolute consistency across runtime versions. For greenfield projects targeting modern Node (14+), you can just use Number.isNaN directly.

This package does exactly one thing: provides a spec-compliant implementation of Number.isNaN for environments that don't have it natively. The learning curve is essentially zero - if you know what Number.isNaN does, you know this package. You import it, call it with a value, and get a boolean back. No configuration, no surprises.

The practical benefit is handling the quirk where global isNaN('string') returns true, while Number.isNaN('string') correctly returns false. This shim behaves like the modern standard, only returning true for actual NaN values. In day-to-day use, it's invisible - which is exactly what you want from a polyfill.

The main consideration is whether you need it at all. Modern browsers and Node.js versions have had Number.isNaN for years. But if you're supporting older environments or want consistent behavior without checking feature support yourself, this package is bulletproof. The codebase is small, well-tested, and maintained by someone deeply involved in JavaScript standards.

This package does exactly one thing: provides a spec-compliant implementation of Number.isNaN. The API is straightforward - import it and use it like the native method. It correctly distinguishes NaN from other non-numeric values, avoiding the pitfall where global isNaN('hello') returns true. TypeScript definitions are included and work flawlessly with IDE autocompletion.

In practice, this is the kind of dependency you add once and never think about again. It's particularly useful when you need to support older environments or want consistent behavior across all runtimes. The implementation is battle-tested and the package has zero dependencies, making it a safe addition to any project.

The main limitation is documentation - the README is sparse. While the API is simple enough that this isn't a major issue, newcomers unfamiliar with the difference between isNaN and Number.isNaN might benefit from more context about why this package exists and when to use it.