Bulk currency change within the whole Google Sheet

Question

I have a "Currency" value cell on the "Cover page" tab with drop-down values "USD, EUR, GBP". What I need is to update the currency format for the whole document(more than 10 tabs with different ranges) by choosing currency value on the "Cover page". Are there any suggestions on how can I do that automatically?

Here are some methods(as an examples), I've tried.

function changeCurrency() {

  var SS = SpreadsheetApp.getActiveSpreadsheet();
  var ss = SS.getSheetByName('Cover Page');
  
  var targetCell = ss.getRange("J8")
  
  var targetSheet = SS.getSheetByName(sheetNameRange);
  
  var range1 = ss.getRange("B8:C200");
  var range2 = ss.getRange("M11:Q13");
  var range3 = ss.getRange("M25:Q40");

  var format1 = "£ 00.00"
  var format2 = "$ 00.00"
  var format3 = "€ 00.00"
if (targetCell = "GBP")
  {range1.setNumberFormat(format1);
  range2.setNumberFormat(format1);
  range3.setNumberFormat(format1);
  }
if (targetCell = "USD")
  {range1.setNumberFormat(format2);
  range2.setNumberFormat(format2);
  range3.setNumberFormat(format2);
  }
else
 {range1.setNumberFormat(format3);
  range2.setNumberFormat(format3);
  range3.setNumberFormat(format3);
  }
}

The first one does not work for me, because ranges with currency format can be changed - new lines can be added, new columns can be added. Also, sheet names can be changed as well by different users.

The second variant I've tried was to change the document's locale. It could be helpful, but new currency applies only if you update the currency for all the ranges with currency format.

  function changeLocale() {
  var SS = SpreadsheetApp.getActiveSpreadsheet();
  var ss = SS.getSheetByName('Cover Page')
  var value = ss.getRange("J8")
if (value = "USD")
{ SS.setSpreadsheetLocale('en_US')
}
if (value = "GBP")
{ SS.setSpreadsheetLocale('en_UK')
}
if (value = "EUR")
{ SS.setSpreadsheetLocale('en_DE')
}
}

Thank you in advance for any options or suggestions regarding this questions.

Answer 1

As I say in my comment, the following script checks every cell number format in the Sheet, and if it contains one of the currency symbols ($, € or £) changes it to the desired one:

function changeCurrencyFormat() {
  const ss = SpreadsheetApp.getActiveSheet()
  const range = ss.getDataRange()
  range.getNumberFormats().forEach((row, idxR) => {
    row.forEach((cellF, idxC) => {
      if (cellF.includes('$') || cellF.includes('€') || cellF.includes('£')) {
        ss.getRange(idxR + 1, idxC + 1).setNumberFormat('€ 00.00')
      }
    })
  })
}

It would be easy to adapt it to your current script to include all the formats.