python-slice-array

python-slice-array.ts

/**
 * Accomodating the JSONPath array range syntax, this is similar to the Python
 * slice function
 */
export function sliceArray<T = unknown>(
  arr: T[],
  start?: number,
  stop?: number,
  step = 1
): T[] {
  // Start coercion
  start = isUndefined(start) || Math.abs(start) === 0 ? 0 : start;
  start = isNegativeNumber(start) ? arr.length - Math.abs(start) : start;

  // Stop coercion
  stop = isUndefined(stop) || Math.abs(stop) === 0 ? arr.length : stop;
  stop = isNegativeNumber(stop) ? arr.length - Math.abs(stop) : stop;

  // Step coercion - JSONPath compat
  step = step === 0 ? 1 : step;

  const slicedArray: T[] = [];

  // JSONPath doesn't support negative steps, neither do we
  if (isNegativeNumber(step)) {
    return slicedArray;
  }

  for (let index = start; index < stop; index += step) {
    slicedArray.push(arr[index]);
  }

  return slicedArray;
}