Error.prototype.cause

The cause data property of an Error instance indicates the specific original cause of the error.

It is used when catching and re-throwing an error with a more-specific or useful error message in order to still have access to the original error.

Value

The value that was passed to the Error constructor in the options.cause argument. It may not be present.

Description

The value of cause can be of any type. You should not make assumptions that the error you caught has an Error as its cause, in the same way that you cannot be sure the variable bound in the catch statement is an Error either. The "Providing structured data as the error cause" example below shows a case where a non-error is deliberately provided as the cause.