NotSupportedError

NotSupportedError is a type of exception used in web standards to indicate that a requested operation cannot be performed in the current context because the environment or user agent does not support it. It is a member of the DOMException family in the Web Platform and is identified by the name NotSupportedError.

NotSupportedError typically arises when a method or API is invoked in an environment where the feature is not implemented or not permitted. This can occur in synchronous code or as a rejected error from asynchronous APIs. In JavaScript, APIs that throw DOMException instances may produce a NotSupportedError when the operation is not supported by the browser, platform, or current configuration.

Properties and handling: NotSupportedError inherits from Error via DOMException and carries standard error properties, such as name and message, and often stack. The code property on DOMException is deprecated in modern APIs. When catching errors, checking the name property (err.name === "NotSupportedError") is a common way to detect this condition and handle it gracefully, such as by falling back to a supported method or informing the user that the feature is unavailable.

Relationship to similar errors: NotSupportedError is distinct from NotAllowedError (which signals permission or policy restrictions) and from NotReadableError or NotInstallableError, which indicate other specific unavailability reasons. Understanding the distinction helps in writing robust feature-detection and graceful degradation strategies.

See also: DOMException, NotAllowedError, NotReadableError.