urlSearchParamsToObj.ts

/**
 * Convert URLSearchParams object to js object
 *
 * Supports arrays so that if the same key is found more than once,
 * convert it to an array.
 *
 * Removes also `[]` characters from the end of a key and sets that
 * key as an array even if there was only one value.
 *
 * @param u url search params to be converted
 * @return js object with the same key-value pairs as u has
 */
export const urlSearchParamsToObj = (
  u: URLSearchParams
): Record<string, string | string[]> => {
  const ret: Record<string, string | string[]> = {};
  u.forEach((value, keyRaw) => {
    const keyIsArray = keyRaw.match(/\[\]$/);
    const key = keyRaw.replace(/\[\]$/, '');
    const current = ret[key];

    if (isArray(current)) {
      current.push(value);
    } else if (keyIsArray) {
      ret[key] = [value];
    } else if (current != null) {
      ret[key] = [current, value];
    } else {
      ret[key] = value;
    }
  });
  return ret;
};