Response: type property

A string, which may be any of the following values:

basic

This applies in any of the following cases:

• The request is same-origin.
• The requested URL's scheme is data:.
• The request's mode is navigate or websocket.

With this type, all response headers are exposed except Set-Cookie.

cors

The request was cross-origin and was successfully processed using CORS. With this type, only CORS-safelisted response headers are exposed.

error

A network error occurred. The status property is set to 0, body is null, headers are empty and immutable.

This is the type of response returned by Response.error(). A response of this type is not returned by a call to fetch(), because if a network error occurs, the promise is rejected.

opaque

A response to a cross-origin request whose mode was set to no-cors. The status property is set to 0, body is null, headers are empty and immutable.

opaqueredirect

A response to a request whose redirect option was set to manual, and which was redirected by the server. The status property is set to 0, body is null, headers are empty and immutable.

The following same-origin request will return a basic response:

const response = await fetch("flowers.jpg");

console.log(response.type); // "basic"

Assuming https://example.org is not the requester's origin, and that the server responds with the appropriate CORS headers, this request will return a cors response:

const response = await fetch("https://example.org/flowers.jpg");

console.log(response.type); // "cors"

The following request is made with the no-cors option, so it returns an opaque response:

const response = await fetch("https://example.org/flowers.jpg", {
  mode: "no-cors",
});

console.log(response.type); // "opaque"
console.log(response.body); // null
console.log(response.status); // 0

The following code uses Response.error() to create an error response:

const response = Response.error();

console.log(response.type); // "error"
console.log(response.body); // null
console.log(response.status); // 0

• ServiceWorker API
• HTTP access control (CORS)
• HTTP