function _ArrayDiff (arr1, arr2) {
    if (arr1.length !== arr2.length) {
      throw RangeError('Not all sub-arrays have the same length')
    }
    const result = []
    const size = arr1.length
    for (let i = 0; i < size; i++) {
      result.push(_ElementDiff(arr1[i], arr2[i]))
    }
    return result
  }
Difference of elements in 2 arrays

@param {Array} arr1     Array 1
@param {Array} arr2     Array 2
@return {Array}         resulting array