Function isCAS

isCAS(cas: unknown): cas is `${string}-${string}-${string}`

Type guard to validate a CAS (Chemical Abstracts Service) number. CAS numbers follow a specific format (XXXXXXX-XX-X) and include a checksum digit.

Parameters

cas: unknown
The CAS number to validate

Returns cas is `${string}-${string}-${string}`

Type predicate indicating if the value is a valid CAS number

Example

isCAS('1234-56-6') // Returns true
isCAS('50-00-0') // Returns true
isCAS('1234-56-999') // Returns false

See

https://www.cas.org/training/documentation/chemical-substances/checkdig

Source

export function isCAS(cas: unknown): cas is CAS<string> {
  if (typeof cas !== "string") return false;
  const regex = RegExp(`^${CAS_REGEX.source}$`);
  const match = cas.match(regex);
  if (!match || !match.groups?.seg_a || !match.groups?.seg_b || !match.groups?.seg_checksum)
    return false;

  const segA = match.groups.seg_a;
  const segB = match.groups.seg_b;
  const segChecksum = match.groups.seg_checksum;

  if (parseInt(segA) === 0 && parseInt(segB) === 0) return false;

  const segABCalc = Array.from(segA + segB)
    .map(Number)
    .reverse()
    .reduce((acc, curr, idx) => acc + (idx + 1) * curr, 0);

  return segABCalc % 10 === Number(segChecksum);
}