code: function getSurrogatePairFromCodePoint(codePoint) {
    const lead = Math.floor((codePoint - 0x10000) / 0x400) + 0xd800;
    const trail = (codePoint - 0x10000) % 0x400 + 0xdc00;
    return {
      lead: lead.toString(16),
      trail: trail.toString(16)
    };
  }
docs: Converts a code point to a surrogate pair.
  Conversion algorithm is taken from The Unicode Standard 3.0 Section 3.7
  (https://www.unicode.org/versions/Unicode3.0.0/ch03.pdf)
  @param {number} codePoint - Between 0x10000 and 0x10ffff
  @returns {{lead: string, trail: string}}