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Response

Baseline Widely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since 2017年3月.

* Some parts of this feature may have varying levels of support.

Fetch API 的Response 介面代表了一個請求會返回的回應。

你可以用Response.Response() 建構子創建一個新的Response物件。但實務上碰到 Response 物件的時機，比較常出現在進行了一個 API 操作後，得到返回的 Response 物件。舉例而言，使用 service workerFetchevent.respondWith 或是使用單純的GlobalFetch.fetch()。

屬性

Response.headersRead only: 包含與此 response 相關的Headers 物件。
Response.okRead only: 無論此 response 是不是成功 ( 狀態碼 200-299 ) 都會包含一個 boolean 狀態。
Response.redirectedRead only: 指出此 response 是不是個重新導向的結果，如果是的話，代表此 URL 具有一個以上的入口。
Response.statusRead only: 包含此 response 的狀態碼(例如：成功時為200 )。
Response.statusTextRead only: 包含狀態碼所對應的狀態文字 (例如：OK 對應200)。
Response.typeRead only: 包含此 response 的類型 (例如：basic,cors)。
Response.urlRead only: 包含此 response 的 URL。
Response.useFinalURL: 包含一個 boolean 狀態，指出此 URL 是否為此 response 的最後一步。

Response 實做了Body, 所以它另有以下可用的屬性：

Body.bodyRead only: A simple getter used to expose aReadableStream of the body contents.
Body.bodyUsedRead only: Stores aBoolean that declares whether the body has been used in a response yet.

方法

Response.clone(): 建立一份Response 的複製物件。
Response.error(): Returns a newResponse object associated with a network error.
Response.redirect(): Creates a new response with a different URL.

Response implementsBody, so it also has the following methods available to it:

Body.arrayBuffer(): Takes aResponse stream and reads it to completion. It returns a promise that resolves with anArrayBuffer.
Body.blob(): Takes aResponse stream and reads it to completion. It returns a promise that resolves with aBlob.
Body.formData(): Takes aResponse stream and reads it to completion. It returns a promise that resolves with aFormData object.
Body.json(): Takes aResponse stream and reads it to completion. It returns a promise that resolves with the result of parsing the body text asJSON.
Body.text(): Takes aResponse stream and reads it to completion. It returns a promise that resolves with aUSVString (text).

在基本 fetch 範例 (run example live) 中，我們使用fetch() 呼叫來得到圖片，並使用<img> tag 顯示。這裡的fetch() 呼叫返回了一個 promise，它使用與資源 fetch 操作有關的Response 進行解析。你可能有發現，由於我們要求的是一張圖片，所以需要用Body.blob (Response 時做了 body) 讓 response 有正確的 MIME 類型。

const image = document.querySelector(".my-image");fetch("flowers.jpg")  .then(function (response) {    return response.blob();  })  .then(function (blob) {    const objectURL = URL.createObjectURL(blob);    image.src = objectURL;  });

除此之外，你也能用Response.Response() 建構子去建立自己的客製化Response 物件：