Google Apps Script to Hide a Row when both of the checkboxes in Col15 and Col18 are checkmarked

In the image, the first checkbox is in Col15 and second checkbox is in Col18. I need that when both the boxes are checkmarked, the row should autohide!

enter image description here

I am very new at it, so could not really get the hang of how to achieve my objective.

If I understood the task correctly, then you can try to hide the row (where both cells in column 15 and 18 are checked) with this script...

function onEdit(e){
  if (e.range.columnStart == 15 && e.source.getActiveSheet().getRange(e.range.rowStart,18).getValue() == true){
    const sheetName = e.source.getActiveSheet().getName();
    var currentRow = e.range.rowStart;
    const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
    const value15 = sheet.getRange(currentRow,15).getValue();
    if (value15){
      sheet.hideRows(currentRow);
    }
} else if (e.range.columnStart == 18 && e.source.getActiveSheet().getRange(e.range.rowStart,15).getValue() == true){
    const sheetName = e.source.getActiveSheet().getName();
    var currentRow = e.range.rowStart;
    const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(sheetName);
    const value18 = sheet.getRange(currentRow,18).getValue();
    if (value18){
      sheet.hideRows(currentRow);
    }
}
}

This is a little bit simplified version:

function onEdit(e){
  if (e.range.columnStart == 15 || e.range.columnStart == 18){
    if (e.source.getActiveSheet().getRange(e.range.rowStart,15).getValue()==true && e.source.getActiveSheet().getRange(e.range.rowStart,18).getValue()==true){
      e.source.getActiveSheet().hideRows(e.range.rowStart);
    }
  } 
}

Update for delete all rows with checked fields in column 15 and 18, executed with menu button...

function onOpen(e) {
  var ui = SpreadsheetApp.getUi()
            .createMenu("Menu")
            .addItem("Hide Checked", "hideChecked")
            .addToUi();
}

function hideChecked(){
  const activeSheetName = SpreadsheetApp.getActiveSpreadsheet().getSheetName();
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(activeSheetName);
  const lastRow = sheet.getLastRow();
  for (var i = lastRow; i > 0 ; i--)
  {
    if (sheet.getRange(i,15).getValue()==true && sheet.getRange(i,18).getValue()==true){
      sheet.hideRows(i);
    }
  }
}