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Message HandlingLearn how messages are parsed when creating a log.

LambdaLog does its best to parse any type of message you can provide it. You may pass in any JSON-stringify-able primitive value as a log such as String, Number, Array, Object, and Boolean, along with any instance of an Error.

Primitive Types

Most primitive types in JavaScript can be stringified into JSON so no additional handling is provided by LambdaLog. Keep in mind that undefined cannot be stringified into JSON and will throw an error.


You may pass in an object as a log message, but there are some limitations. It's best to use plain objects when possible.

  • If the object is a class and has anything on the prototype, these values will not be included in the message.
  • Objects containing circular references will be truncated.


In many cases, you may log an Error that occurred within your application. Errors may be passed in as the log message for any log level. LambdaLog determines if the provided value is an error by checking:

  • The value is an object AND it's an instance of Error.
  • The value is an object AND it has a message and stack property.

If LambdaLog determines the value is an error, there is a few things that will happen:

  • The log message is set to the value of the message property.
  • A stack property is added to the metadata for the log with the value of the error's stack property.
  • A name property is added to the metadata for the log with the value of the error's name property.
  • Any additional properties on the error object that is not on the prototype will be added to the log's metadata.