openById

openById is a method used in Google Apps Script to open a Google Drive file by its unique identifier. It is implemented in several Apps Script services, most commonly DocumentApp, SpreadsheetApp, and SlidesApp, and it returns a service-specific object that represents the opened file.

When you call openById with a file’s ID, Apps Script resolves the ID and returns an object of the corresponding type, such as a Document, Spreadsheet, or Presentation. This object then provides methods to interact with the file, for example accessing its content, metadata, or structure. If the file type is not compatible with the service or the ID is invalid, the call throws an error. The script must be authorized with the appropriate scope to access the file.

Typical usage includes opening documents, spreadsheets, or presentations by ID, then performing further operations. For example, a document can be opened with DocumentApp.openById(id) and browsed via getBody() or getName(); a spreadsheet can be opened with SpreadsheetApp.openById(id) to access sheets and ranges; a presentation can be opened with SlidesApp.openById(id) to manipulate slides. It is important to note that the script must have permission to access the file, which may require sharing or domain-level access.

Alternatives to openById include openByUrl, which takes a full URL to the file, and using DriveApp methods to retrieve a file by ID before performing type-specific operations.