How can I use a block optional in mask?

[rebroff]

I want to make the "to" block optional in a date range.

const dateMaskOptions = {
  mask: Date,
  blocks: {
    d: {
      mask: IMask.MaskedRange,
      placeholderChar: 'D',
      from: 1,
      to: 31,
      maxLength: 2,
    },
    m: {
      mask: IMask.MaskedRange,
      placeholderChar: 'M',
      from: 1,
      to: 12,
      maxLength: 2,
    },
    Y: {
      mask: IMask.MaskedRange,
      placeholderChar: 'Y',
      from: new Date().getFullYear() - 10,
      to: new Date().getFullYear(),
      maxLength: 4,
    },
  },
}

const dateRangeMaskOptions = {
  mask: [
    {
      mask: 'from[-to]',
      blocks: {
        from: dateMaskOptions,
        to: dateMaskOptions,
      },
    },
  ],
};

It doesn't work the way I want it to. The problem is that the "to" block is still required.