Google Sheets - Unmerge cells and fill down - google-sheets

Question

I need to take a sheet maintained by someone else and do the following (so that I can export to a csv):
unmerge all cells
fill values down
merged cells are in multiple columns, so I need to iterate over a range
It's too much to do it by hand, and it will need done periodically. My javascript and google sheets object model knowledge approximate zero, but I know it's possible because I could do it in VBA. I searched but can only find programmatic answers for VBA/Excel.
How can I do this efficiently in Google Sheets?

Answer 1

You can use the breakapart() class to do this. I am assuming that the merged range is not static and has multiple occurrences. This script will unmerge all merged ranges in the active sheet.
function myFunction() {
var sheet = SpreadsheetApp.getActiveSheet();
sheet.getRange(1, 1, sheet.getMaxRows(), sheet.getMaxColumns()).breakApart();
}

Answer 2

Adapted from #lreeder's answer
The following breaks and fill blank with above on the selected range:
function onOpen() {
var ui = SpreadsheetApp.getUi();
// Or DocumentApp or FormApp.
ui.createMenu('BreakAndFill')
.addItem('Break Fill Blank Cells', 'menuItem1')
.addToUi();
}
function menuItem1() {
BreakandfillBlankWithAbove()
}
//Breaks range
//Iterates over the range from top to bottom
//and left to right, and fills blank cells
//with the value right above them.
function BreakandfillBlankWithAbove() {
var sheet = SpreadsheetApp.getActiveSheet();
var range = sheet.getActiveRange();
Logger.log('Range height is: ' + range.getHeight());
var values = range.getValues();
range.breakApart();
var width = values[0].length;
var height = values.length;
Logger.log('Width is ' + width);
Logger.log('Height is ' + height);
for (var i = 0; i < width; i++) {
var lastVal = '';
for(var j = 0; j < height; j++) {
var currValue = values[j][i];
var dataType = typeof(currValue);
//Empty string check returns true if dataType
//is a number, and value is zero. In that case
//we don't want to overwrite the zero, so only
//check emptyString for string types.
if(currValue === undefined ||
(dataType === 'string' && currValue == '')
) {
//getCell parameters are relative to the current range
//and ones based
var cell = range.getCell(j+1, i+1);
cell.setValue(lastVal);
}
else {
lastVal = currValue;
}
}
}
SpreadsheetApp.flush();
}