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  4. Response

Response

The Response interface represents an HTTP response and is part of the Fetch API.

​​ Constructor

let response = new Response(body, init);

​​ Parameters

Valid options for the options object include:

  • cf any | null

    • An object that contains Cloudflare-specific information. This object is not part of the Fetch API standard and is only available in Cloudflare Workers. This field is only used by consumers of the Response for informational purposes and does not have any impact on Workers behavior.

  • encodeBody string

    • Workers have to compress data according to the content-encoding header when transmitting, to serve data that is already compressed, this property has to be set to "manual", otherwise the default is "automatic".

  • headers Headers | ByteString

  • status int

    • The status code for the response, such as 200.

  • statusText string

    • The status message associated with the status code, such as, OK.

  • webSocket WebSocket | null

    • This is present in successful WebSocket handshake responses. For example, if a client sends a WebSocket upgrade request to an origin and a Worker intercepts the request and then forwards it to the origin and the origin replies with a successful WebSocket upgrade response, the Worker sees response.webSocket. This establishes a WebSocket connection proxied through a Worker. Note that you cannot intercept data flowing over a WebSocket connection.

​​ Properties

  • response.body Readable Stream

    • A getter to get the body contents.

  • response.bodyUsed boolean

    • A boolean indicating if the body was used in the response.

  • response.headers Headers

    • The headers for the response.

  • response.ok boolean

    • A boolean indicating if the response was successful (status in the range 200-299).

  • response.redirected boolean

    • A boolean indicating if the response is the result of a redirect. If so, its URL list has more than one entry.

  • response.status int

    • The status code of the response (for example, 200 to indicate success).

  • response.statusText string

    • The status message corresponding to the status code (for example, OK for 200).

  • response.url string

    • The URL of the response. The value is the final URL obtained after any redirects.

  • response.webSocket WebSocket?

    • This is present in successful WebSocket handshake responses. For example, if a client sends a WebSocket upgrade request to an origin and a Worker intercepts the request and then forwards it to the origin and the origin replies with a successful WebSocket upgrade response, the Worker sees response.webSocket. This establishes a WebSocket connection proxied through a Worker. Note that you cannot intercept data flowing over a WebSocket connection.

​​ Methods

​​ Instance methods

  • clone() : Response

  • json() : Response

    • Creates a new response with a JSON-serialized payload.

  • redirect() : Response

    • Creates a new response with a different URL.

​​ Additional instance methods

Response implements the Body mixin of the Fetch API, and therefore Response instances additionally have the following methods available:

​​ Set the Content-Length header

The Content-Length header will be automatically set by the runtime based on whatever the data source for the Response is. Any value manually set by user code in the Headers will be ignored. To have a Content-Length header with a specific value specified, the body of the Response must be either a FixedLengthStream or a fixed-length value just as a string or TypedArray.

A FixedLengthStream is an identity TransformStream that permits only a fixed number of bytes to be written to it.

  const { writable, readable } = new FixedLengthStream(11);


  const enc = new TextEncoder();
  const writer = writable.getWriter();
  writer.write(enc.encode("hello world"));
  writer.end();


  return new Response(readable);

Using any other type of ReadableStream as the body of a response will result in chunked encoding being used.