@ABG I tried both, it was very slow either way.
@TIMAI2 Thank you so much for your help !
I am having trouble changing your app to read my spreadsheet.
Here is what I get when I press the button write :
Here is the modified version of your app :
Script
function doGet(e) {
// ### Write INPUT to A1 to E6 on Sheet2 ###
if(e.parameter.func == "WRITE") {
var ss = SpreadsheetApp.getActive();
var sh = ss. getSheetByName("Sheet2");
sh.clearContents();
sh.appendRow([e.parameter.a1,e.parameter.a2,e.parameter.a3,e.parameter.a4,e.parameter.a5,e.parameter.a6]);
return ContentService.createTextOutput("Data Successfully Written");
}// ### Read OUTPUT from B1 to B6 on Sheet1 ###
else if(e.parameter.func == "READ") {
var ss = SpreadsheetApp.getActive();
var sh = ss.getSheetByName("Sheet1");
var rg = sh.getRange("B1:B6").getValues();
var outString = ;
for(var row=0; row<5 ; ++row){
outString.push(rg[row]);
}return ContentService.createTextOutput(outString); // will return a1,a2,a3,a4,a5 //return ContentService.createTextOutput(JSON.stringify(outString)); // will return [[a1],[a2],[a3],[a4],[a5]]}
}
Spreadsheet
AIA
SimpleReadWrite_copy.aia (3.6 KB)
Edit : I tried to redo the same spreadsheet as yours and I end up with the same problem.

