Google Apps Script: How to expand columns based on unique column members?

Question

I have to transpose the 4 unique dates into 4 columns in another sheet. The other sheet only has two columns and will need to add 2 more columns to accommodate the transpose using insertColumns.

How can I achieve this using only Google Apps Script wherein the scripts checks whether the sheet has enough columns and inserts them accordingly if not?

function unique() {

  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getSheetByName("Sheet1");
  var lrow = sheet.getLastRow();
  var range = sheet.getRange(2, 1, lrow-1, 1).getValues();
  var unique = [...new Set(range)]

  Logger.log(unique.length);  // Not returning unique length - 7.0

}

Answer 1

Unique Dates

function unique() {
  var ss = SpreadsheetApp.getActive();
  var sh = ss.getSheetByName("Sheet0");
  var vs = sh.getRange(2, 1, sh.getLastRow() - 1).getValues().flat().map(d => d.valueOf());
  var uvs = [...new Set(vs)].map(v => new Date(v));
  if(sh.getMaxColumns() < uvs.length) {
    sh.insertColumnsAfter(sh.getLastColumn(), uvs.length - sh.getLastColumn() - 1)
  }
  sh.clearContents();
  sh.getRange(2,1,1,uvs.length).setValues([uvs]);
}

Before:

Date
1/1/2022
1/2/2022
1/3/2022
1/4/2022
1/4/2022
1/4/2022
1/4/2022
1/4/2022
1/4/2022
1/4/2022

After:

1/1/2022	1/2/2022	1/3/2022	1/4/2022