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Reserved Methods

Some method names are reserved or have special semantics.

​​ Special Methods

For backwards compatibility, when extending WorkerEntrypoint or DurableObject, the following method names have special semantics. Not that this does not apply to RpcTarget. On RpcTarget, these methods work like any other RPC method.

​​ fetch()

The fetch() method is treated specially — it can only be used to handle an HTTP request — equivalent to the fetch handler.

You may implement a fetch() method in your class that extends WorkerEntrypoint — but it must accept only one parameter of type Request, and must return an instance of Response, or a Promise of one.

On the client side, fetch() called on a service binding or Durable Object stub works like the standard global fetch(). That is, the caller may pass one or two parameters to fetch(). If the caller does not simply pass a single Request object, then a new Request is implicitly constructed, passing the parameters to its constructor, and that request is what is actually sent to the server.

Some properties of Request control the behavior of fetch() on the client side and are not actually sent to the server. For example, the property redirect: "auto" (which is the default) instructs fetch() that if the server returns a redirect response, it should automatically be followed, resulting in an HTTP request to the public internet. Again, this behavior is according to the Fetch API standard. In short, fetch() doesn’t have RPC semantics, it has Fetch API semantics.

​​ connect()

The connect() method of the WorkerEntrypoint class is reserved for opening a socket-like connection to your Worker. This is currently not implemented or supported — though you can open a TCP socket from a Worker or connect directly to databases over a TCP socket with Hyperdrive.

​​ Disallowed Method Names

The following method (or property) names may not be used as RPC methods on any RPC type (including WorkerEntrypoint, DurableObject, and RpcTarget):

  • dup: This is reserved for duplicating a stub. Refer to the RPC Lifecycle docs to learn more about dup().
  • constructor: This name has special meaning for JavaScript classes. It is not intended to be called as a method, so it is not allowed over RPC.

The following methods are disallowed only on WorkerEntrypoint and DurableObject, but allowed on RpcTarget. These methods have historically had special meaning to Durable Objects, where they are used to handle certain system-generated events.

  • alarm
  • webSocketMessage
  • webSocketClose
  • webSocketError