function removeDuplicates() {
  const startTime = new Date();
  const newData = [];
  const sheet = SpreadsheetApp.getActiveSheet();
  const data = sheet.getDataRange().getValues();
  const numRows = data.length;
  const seen = {};

  for (var i = 0, row, key; i < numRows && (row = data[i]); i++) {
    key = JSON.stringify(row);
    if (key in seen) {
      continue;
    }
    seen[key] = true;
    newData.push(row);
  };