Function sample

random/sample.ts:56–97

(
  array: ArrayLike<T>,
  options?: SampleOptions,
)

 * ```
 */
export function sample<T>(
  array: ArrayLike<T>,
  options?: SampleOptions,
): T | undefined {
  const { weights } = { ...options };

  if (weights) {
    if (weights.length !== array.length) {
      throw new RangeError(
        "Cannot sample an item: The length of the weights array must match the length of the input array",
      );
    }

    if (!array.length) return undefined;

    const total = Object.values(weights).reduce((sum, n) => sum + n, 0);

    if (total <= 0) {
      throw new RangeError(
        "Cannot sample an item: Total weight must be greater than 0",
      );
    }

    const rand = (options?.prng ?? Math.random)() * total;
    let current = 0;

    for (let i = 0; i < array.length; ++i) {
      current += weights[i]!;
      if (rand < current) {
        return array[i]!;
      }
    }

    // this line should never be hit, but in case of rounding errors etc.
    return array[0]!;
  }

  const length = array.length;
  return length
    ? array[randomIntegerBetween(0, length - 1, options)]
    : undefined;
}