docs: function (arr, ct, key) {
          // Deal with situation, e.g., if encounter index 4 and try
          // to set it to 0, but 0 exists later in loop (need to
          // increment all subsequent (skipping current key, since
          // we need its value below) until find unused)
          if (arr[ct] !== undefined) {
            var tmp = ct
            ct += 1
            if (ct === key) {
              ct += 1
            }
            ct = _checkToUpIndices(arr, ct, key)
            arr[ct] = arr[tmp]
            delete arr[tmp]
          }
      
          return ct
        }