Why does ss.deleteSheet() unhide one hidden sheet - google-apps-script

Question

I've written a little script that automatically deletes all Sheets my user accidentally create.
Often, when accessing the spreadsheet with their phone, they accidentally click on "+" and create tons of empty sheets, like Sheet101, Sheet102, etc.
My script is very simple: gets all sheets, and if the name starts with Sheet, just deletes it.
It works perfectly, but after deleting all the undesired sheets, the problem is that it automatically unhides the first hidden sheet (some sheets are hidden for practical use, like they contain lists).
For example, if I have the following hidden sheets:
oldform, list1, list2, ...
After executing the script, the sheet oldform will be unhidden, thus appearing to the users.
Here is two codes I've tried:
The simple one:
function DELETESHEETS2() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheets = ss.getSheets();
for (i = 0; i < sheets.length; i++) {
if ( sheets[i].getName().indexOf("Sheet") > -1 ) {
ss.deleteSheet(sheets[i]);
}
}
}
The one I tried to modify to solve my problem:
function DELETESHEETS3() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheets = ss.getSheets();
for (i = 0; i < sheets.length; i++) {
if ( sheets[i].getName().indexOf("Sheet") > -1 ) {
label = sheets[i].getName();
toto = ss.getSheetByName(label);
ss.deleteSheet(toto);
}
}
}
The reverse loop
With this one, the hidden sheet appears at the beginning and not at the end:
function DELETESHEETS2() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheets = ss.getSheets();
for (i = sheets.length -1; i > 0 ; i--) {
if ( sheets[i].getName().indexOf("Sheet") > -1 ) {
ss.deleteSheet(sheets[i]);
}
}
}
A partial solution
This one works, thanks to #OMila. But it does not explain the weird behavior of a simple loop. Maybe I missed something?
function DELETESHEETS2() {
var ss = SpreadsheetApp.getActiveSpreadsheet();
var sheets = ss.getSheets();
var hdnShts = [];
for (var i = 0; i < sheets.length; i++) {
if(sheets[i].isSheetHidden()) {
hdnShts.push(sheets[i].getName()); //saving all the hidden sheet names for later
}
}
for (i = 0; i < sheets.length; i++) {
if ( sheets[i].getName().indexOf("Sheet") > -1 ) {
ss.deleteSheet(sheets[i]);
}
}
for(var i = 0; i<hdnShts.length; i++) {
ss.getSheetByName(hdnShts[i]).hideSheet(); //just to make sure all the hiddens remain hidden
}
}
Thanks for your help if you have any idea!
PS: this problem is easy to reproduce, just create lots of sheets including one with a name other than Sheetxxx

Answer 1

Try this:
function delSheetsKeepHidden() {
var ss = SpreadsheetApp.getActive();
var shts = ss.getSheets();
var hdnShts = [];
for (var i = 0; i < shts.length; i++) {
if(shts[i].isSheetHidden()) {
hdnShts.push(shts[i].getName()); //saving all the hidden sheet names for later
}
}
for(var i = 0; i < shts.length; i++) {
if(shts[i].getName().slice(0,5).toLowerCase() == "sheet") {
ss.deleteSheet(shts[i]); //I think this is just deleting the sheet and not the array element in shts so no reason to keep track of deleted sheets like when deleting rows in a spreadsheet
}
}
for(var i = 0; i<hdnShts.length; i++) {
ss.getSheetByName(hdnShts[i]).hideSheet(); //just to make sure all the hiddens remain hidden
}
}
I've been forcing myself to get away from old school loops.
function delSheetsKeepHidden() {
var ss=SpreadsheetApp.getActive();
var shts=ss.getSheets();
var hdnShts=[];
shts.forEach(function(sht){if(sht.isSheetHidden()){hdnShts.push(sht.getName())}});
shts.forEach(function(sht){if(sht.getName().slice(0,5).toLowerCase()=="sheet"){ss.deleteSheet(sht);}});//I think this is just deleting the sheet and not the array element in shts so no reason to keep track of deleted sheets like when deleting rows in a spreadsheet
hdnShts.forEach(function(name){ss.getSheetByName(name).hideSheet();});//just to make sure all the hiddens remain hidden
}