Errors

ransu throws exactly one error type. code is for programs, message is for people, and every message says what to do instead.

import { RansuError } from "ransu";

try {
  pick([]);
} catch (error) {
  if (error instanceof RansuError && error.code === "EMPTY_COLLECTION") {
    // …
  }
}

Code	Trigger
EMPTY_COLLECTION	Picking from an empty collection
INVALID_ARGUMENT	A parameter is the wrong shape or out of bounds
INVALID_RANGE	min > max, or an empty range
INVALID_WEIGHTS	Negative, NaN, all-zero, or a length mismatch
NOT_INTEGER	A non-integer where an integer is required
NO_CRYPTO	The runtime has no CSPRNG and a secure API was called
RANGE_TOO_LARGE	A range wider than 2^53 asked of an integer API
SAMPLE_TOO_LARGE	k > n without replacement
STATE_MISMATCH	Restoring state into a different algorithm or version
UNSEEDABLE_ENGINE	Seeding something that must not be seeded

No silent fallbacks

Bounds are never swapped, ranges are never truncated, and a missing CSPRNG never degrades to Math.random. Each of those would produce plausible-looking output that is quietly wrong, which is worse than a stack trace.