mgrs.js
function get100kID(easting, northing, zoneNumber) {
  const setParm = get100kSetForZone(zoneNumber);
  const setColumn = Math.floor(easting / 100000);
  const setRow = Math.floor(northing / 100000) % 20;
  return getLetter100kID(setColumn, setRow, setParm);
}
function get100kID(easting, northing, zoneNumber) {
  const setParm = get100kSetForZone(zoneNumber);
  const setColumn = Math.floor(easting / 100000);
  const setRow = Math.floor(northing / 100000) % 20;
  return getLetter100kID(setColumn, setRow, setParm);
}
function get100kID ( easting , northing , zoneNumber ) { const setParm = get100kSetForZone ( zoneNumber ) ; const setColumn = Math . floor ( easting / 100000 ) ; const setRow = Math . floor ( northing / 100000 ) % 20 ; return getLetter100kID ( setColumn , setRow , setParm ) ; }
Get the two letter 100k designator for a given UTM easting,
northing and zone number value.

@private
@param {number} easting
@param {number} northing
@param {number} zoneNumber
@return {string} the two letter 100k designator for the given UTM location.
Get the two letter 100k designator for a given UTM easting northing and zone number value .