[Apps Script] Getting the unmerged ranges within a range

UnmergedRanges.gs

/**
 * Gets all the unmerged ranges within a range.
 * @param {SpreadsheetApp.Range} range The range to evaluate.
 * @returns {SpreadsheetApp.Range[]} The unmerged ranges.
 */
function getUnmergedRanges(range) {
  if (!range.isPartOfMerge()) {
    return [range];
  }
  var mergedRanges = range.getMergedRanges();
  var ranges = [range];
  mergedRanges.forEach(function(mergedRange) {
    ranges = ranges.reduce(function(result, range) {
      return result.concat(subtractRange(range, mergedRange));
    }, []);
  });
  return ranges;
}

/**
 * Subtracts one range from another.
 * @param {SpreadsheetApp.Range} minuend The range to subtract from.
 * @param {SpreadsheetApp.Range} subtrahend The range to subtract.
 * @returns {SpreadsheetApp.Range[]} The resulting ranges.
 */
function subtractRange(minuend, subtrahend) {
  var intersection = getIntersection(minuend, subtrahend);
  if (!intersection) {
    return [minuend];
  }
  var sheet = minuend.getSheet();
  var result = [];
  // Top slice.
  if (subtrahend.getRow() > minuend.getRow()) {
    var top = getRangeWithStartAndEnd(sheet, minuend.getRow(), minuend.getColumn(), 
        subtrahend.getRow() - 1, minuend.getLastColumn());
    result.push(top);
  }
  // Bottom slice.
  if (subtrahend.getLastRow() < minuend.getLastRow()) {
    var bottom = getRangeWithStartAndEnd(sheet, subtrahend.getLastRow() + 1, minuend.getColumn(), 
        minuend.getLastRow(), minuend.getLastColumn());
    result.push(bottom);
  }
  // Left slice.
  if (subtrahend.getColumn() > minuend.getColumn()) {
    var left = getRangeWithStartAndEnd(sheet, 
        Math.max(minuend.getRow(), subtrahend.getRow()), 
        minuend.getColumn(), 
        Math.min(minuend.getLastRow(),subtrahend.getLastRow()), 
        subtrahend.getColumn() - 1);
    result.push(left);
  }
  // Right slice.
  if (subtrahend.getLastColumn() < minuend.getLastColumn()) {
    var right = getRangeWithStartAndEnd(sheet, 
        Math.max(minuend.getRow(), subtrahend.getRow()), 
        subtrahend.getLastColumn() + 1, 
        Math.min(minuend.getLastRow(), subtrahend.getLastRow()), 
        minuend.getLastColumn());
    result.push(right);
  }
  return result;
}

/**
 * Gets the intersection of two ranges.
 * @param {SpreadsheetApp.Range} range1 One range.
 * @param {SpreadsheetApp.Range} range2 The other range.
 * @returns {SpreadsheetApp.Range} A range representing the intersection, or null if they don't intersect.
 */
function getIntersection(range1, range2) {
  if (range1.getSheet().getSheetId() != range2.getSheet().getSheetId()) {
    return null;
  }
  var sheet = range1.getSheet();
  var startRow = Math.max(range1.getRow(), range2.getRow());
  var endRow = Math.min(range1.getLastRow(), range2.getLastRow());
  var startColumn = Math.max(range1.getColumn(), range2.getColumn());
  var endColumn = Math.min(range1.getLastColumn(), range2.getLastColumn());
  if (startRow > endRow || startColumn > endColumn) {
    return null;
  }
  return getRangeWithStartAndEnd(sheet, startRow, startColumn, endRow, endColumn);
}

/**
 * Gets the difference between two ranges.
 * @param {SpreadsheetApp.Range} range1 One range.
 * @param {SpreadsheetApp.Range} range2 The other range.
 * @returns {SpreadsheetApp.Range[]} The ranges representing the difference.
 */
function getDifference(range1, range2) {
  var intersection = getIntersection(range1, range2);
  if (!intersection) {
    return [range1, range2];
  }
  return [range1, range2].reduce(function(result, range) {
    return result.concat(subtractRange(range, intersection));
  }, []);
}

/**
 * Gets a range specified using end rows and columns, instead of widths and heights.
 * @param {SpreadsheetApp.Sheet} sheet The sheet containing the range.
 * @param {Number} startRow The start row (1-indexed).
 * @param {Number} startColumn The start column (1-indexed).
 * @param {Number} endRow The end row (1-indexed).
 * @param {Number} endColumn The end column (1-indexed).
 * @returns {SpreadsheetApp.Range} The range.
 */
function getRangeWithStartAndEnd(sheet, startRow, startColumn, endRow, endColumn) {
  return sheet.getRange(startRow, startColumn, endRow - startRow + 1, endColumn - startColumn + 1);
}