Class Logger

AI-generated Key Takeaways

• The Logger class enables developers to write text to debugging logs for script analysis and troubleshooting.

• It provides methods to clear the log, retrieve the entire log as a string, and write formatted or unformatted messages to the log.

• Logged output can be viewed within the Apps Script editor using "View > Show logs" and utilized for debugging purposes.

• The getLog() method allows for capturing the log content, which can then be used for saving, emailing, or further processing.

• Developers can leverage format strings and values to create structured log messages using the log(format, values) method.

Logger

This class allows the developer to write to the Execution log and to Google Cloud Logging if the script is associated with a standard Cloud Project. This class is preferred for structured logging and jsonPayload support in Cloud Logging. For time-based logging, use console.

Methods

Method	Return type	Brief description
clear()	void	Clears the log.
getLog()	String	Returns a complete list of messages in the current log.
log(data)	Logger	Writes the data to the log.
log(format, values)	Logger	Writes a formatted string to the logging console, using the format and values provided.

Detailed documentation

clear()

Clears the log.

---

getLog()

Returns a complete list of messages in the current log. This method can be used to save or email the entire log output generated during script execution.

// Generate a log, then email it to the person who ran the script.
const files = DriveApp.getFiles();
while (files.hasNext()) {
  Logger.log(files.next().getName());
}
const recipient = Session.getActiveUser().getEmail();
const subject = 'A list of files in your Google Drive';
const body = Logger.getLog();
MailApp.sendEmail(recipient, subject, body);

Return

String — the log from the logging console

---

log(data)

Writes the data to the log. The data can be a string, a JavaScript object, or an object with a message property.

Logger.log("my log message");
// Info   my logmessage
Logger.log({ key: "value" });
// Info   {key=value}
Logger.log({ message: "my log message", data: { key: "value" } })
// Info   my logmessage

When passing an object, if the object contains a message property, that property is used as the log message. Otherwise, the toString() method is called to convert the object to a string. All other properties which are JSON serializable are included as part of the jsonPayload in the LogEntry, similar to the example below:

{
  "insertId": "w5eib...",
  "jsonPayload": {
    "message": "my log message",
    "serviceContext": {
      "service": "AKfyc..."
    },
    "data": {
      "key": "value"
    }
  },
  "resource": {
    "type": "app_script_function",
    "labels": {
      "invocation_type": "editor",
      "function_name": "unknown",
      "project_id": "1234567890"
    }
  },
  "timestamp": "2024-11-15T23:28:19.448591Z",
  "severity": "INFO",
  "labels": {
    "script.googleapis.com/user_key": "AOX2d...",
    "script.googleapis.com/process_id": "EAEA1...",
    "script.googleapis.com/project_key": "MQXvl...",
    "script.googleapis.com/deployment_id": "AKfyc..."
  },
  "logName": "projects/[PROJECT_ID]/logs/script.googleapis.com%2Fconsole_logs",
  "receiveTimestamp": "2024-11-15T23:28:20.363790313Z"
}

Parameters

Name	Type	Description
data	Object	the object to log

Return

Logger — the Logger, for chaining.

---

log(format, values)

Writes a formatted string to the logging console, using the format and values provided. The string can include multiple %s placeholders, which are replaced with corresponding values from the list of arguments, converted to strings.

// Log the number of Google Groups you belong to.
const groups = GroupsApp.getGroups();
Logger.log('You are a member of %s Google Groups.', groups.length);

Parameters

Name	Type	Description
format	String	a format string that contains as many instances of %s as the number of values arguments
values	Object...	a variable number of values to insert into the format string

Return

Logger — the Logger, for chaining