sorting columns independently at array level - google-apps-script

Question

I have a spreadsheet with several columns that I need to sort individually.
I wrote the script below that works but is a bit slow since it handles each column in turn with getValues() and setValues().
I'd like to find a way to do the whole sorting at an array level for more efficiency but I don't know how... any suggestion ?
Here is the relevant part of the code I use now :
...
sh3.getRange(1,1,1,newData[0].length).setFontWeight('bold');// newData is an array corresponding to the whole sheet
for(col=1;col<newData[0].length;++col){
var val = sh3.getRange(2,col,getLastRowInCol(col),1).getValues().sort();// each column have a different height
sh3.getRange(2,col,getLastRowInCol(col),1).setValues(val)
}
}
function getLastRowInCol(col){
var values = sh3.getRange(2,col,sh3.getLastRow(),1).getValues();// skip header and find last non empty row in column
for(n=0;n<values.length;++n){
if(values[n]==''){break}
}
return n
}
Note : I know there is a Library by Romain Vialard that does the job (sorting columns in 2D arrays) but I'm interrested on how to do it 'manually' for personal JS skills improvement ;-) and also I need to sort every column independently without needing to update the sheet for every column.

Answer 1

How about:
function sortColumns() {
var sheet = SpreadsheetApp.getActiveSheet();
var startRow = 2;
var startCol = 1;
var dataRange = sheet.getRange(startRow, startCol, sheet.getLastRow() - startRow + 1, sheet.getLastColumn() - startCol + 1);
var data = dataRange.getValues();
// transpose data so each column item will be listed in an single array
// for each column so that it can be sorted with array.sort()
var rowToCol = [];
for (var i = 0; i < data[0].length; i++) {
rowToCol.push([]);
for (var j = 0; j < data.length; j++) {
// replace empty string with undefined as undefined sorts last
rowToCol[i].push(data[j][i]==""?undefined:data[j][i]);
}
rowToCol[i].sort();
// default sort, as above, is alphabetic ascending. For other methods
// search for Javascript array sort functions
}
// transpose sorted items back to their original shape
var result = [];
for (var i = 0; i < rowToCol[0].length; i++) {
result.push([]);
for (var j = 0; j < rowToCol.length; j++) {
result[i].push(rowToCol[j][i]==undefined?"":rowToCol[j][i]);
}
}
dataRange.setValues(result);
};
function onOpen() {
var sheet = SpreadsheetApp.getActiveSpreadsheet();
var entries = [{
name : "Sort Columns",
functionName : "sortColumns"
}];
sheet.addMenu("Script Center Menu", entries);
};