Google Apps Script, Google Sheets - Getting Spreadsheet ID and Sheet ID programmatically

I've been reading this without making any headway:

https://developers.google.com/apps-script/reference/spreadsheet/spreadsheet-app

Is there a way to programmatically get the Spreadsheet ID and Sheet ID of a particular Google SpreadSheet's sheet without manually typing or copying the URL?

1.) If the script is bound to the spreadsheet then you can just use getID and getSheetID as mentioned by TheMaster in the comments. See codes below:

function getIDs() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var sheet = ss.getActiveSheet();
  var spreadSheetID = ss.getId();
  var sheetID = sheet.getSheetId();
  console.log(spreadSheetID);
  console.log(sheetID);
}

Result:

Take note that the first sheet always has an ID of 0 (gid=0) as the default value.

2.) Otherwise if what you are trying to do is get the Spreadsheet ID and Sheet ID from different spreadsheets it is not possible without copying the URL since there is no way it can identify which spreadsheet to refer to.

3.) Suggestion

What you can do if you need to get IDs of different files is to move them to a folder in your drive, then you can use the code below:

function listFilesInFolder(folderName) {
  
  var sheet = SpreadsheetApp.getActiveSheet();
  sheet.getRange(1,1,sheet.getLastRow(),sheet.getLastColumn()).clearContent();
  
  sheet.appendRow(["Name", "Spreadsheet ID", "Sheet ID"]);

  //change the folder ID below to reflect your folder's ID (look in the URL when you're in your folder)
  var folder = DriveApp.getFolderById("HIS_SHOULD_BE_YOUR_FOLDER_ID");
  var contents = folder.getFiles();

  var cnt = 0;
  var file;

  while (contents.hasNext()) {
    var file = contents.next();
    cnt++;

    data = [
      file.getName(),
      file.getId(),
    ];

    var spreadsheetSheets = SpreadsheetApp.openById(data[1]).getSheetByName("Sheet2").getSheetId();
    data.push(spreadsheetSheets);
    sheet.appendRow(data);
  };
};

Folder:

Result:

Note: In my example code I've made use of Sheet2 to see that it is working as expected. Please set accordingly to the name of the sheet which you are trying to get the ID.

Let me know if this works for you or if you have other questions.

References:

• Are Google Spreadsheets' first sheets always given an ID of 0?
• Getting all files ID in drive folder