Response
The Response
interface of the Fetch API represents the response to a request.
You can create a new Response
object using the Response.Response()
constructor, but you are more likely to encounter a Response
object being returned as the result of another API operation—for example, a service worker Fetchevent.respondWith
, or a simple WindowOrWorkerGlobalScope.fetch()
.
Constructor
Response()
- Creates a new
Response
object.
Properties
Response.headers
Read only- The
Headers
object associated with the response. Response.ok
Read only- A boolean indicating whether the response was successful (status in the range
200
–299
) or not. Response.redirected
Read only- Indicates whether or not the response is the result of a redirect (that is, its URL list has more than one entry).
Response.status
Read only- The status code of the response. (This will be
200
for a success). Response.statusText
Read only- The status message corresponding to the status code. (e.g.,
OK
for200
). Response.trailers
- A
Promise
resolving to aHeaders
object, associated with the response withResponse.headers
for values of the HTTPTrailer
header. Response.type
Read only- The type of the response (e.g.,
basic
,cors
). Response.url
Read only- The URL of the response.
Body Interface Properties
Response
implements Body
, so it also has the following properties available to it:
Body.body
Read only- A simple getter exposing a
ReadableStream
of the body contents. Body.bodyUsed
Read only- Stores a
Boolean
that declares whether the body has been used in a response yet.
Methods
Response.clone()
- Creates a clone of a
Response
object. Response.error()
- Returns a new
Response
object associated with a network error. Response.redirect()
- Creates a new response with a different URL.
Body Interface Methods
Response
implements Body
, so it also has the following methods available to it:
Body.arrayBuffer()
- Takes a
Response
stream and reads it to completion. It returns a promise that resolves with anArrayBuffer
. Body.blob()
- Takes a
Response
stream and reads it to completion. It returns a promise that resolves with aBlob
. Body.formData()
- Takes a
Response
stream and reads it to completion. It returns a promise that resolves with aFormData
object. Body.json()
- Takes a
Response
stream and reads it to completion. It returns a promise that resolves with the result of parsing the body text asJSON
, which is a JavaScript value of datatype object, string, etc. Body.text()
- Takes a
Response
stream and reads it to completion. It returns a promise that resolves with aUSVString
(text).
Examples
Fetching an image
In our basic fetch example (run example live) we use a simple fetch()
call to grab an image and display it in an <img>
element. The fetch()
call returns a promise, which resolves to the Response
object associated with the resource fetch operation.
You'll notice that since we are requesting an image, we need to run Body.blob
(Response
implements Body) to give the response its correct MIME type.
const image = document.querySelector('.my-image');
fetch('flowers.jpg')
.then(response => response.blob())
.then(blob => {
const objectURL = URL.createObjectURL(blob);
image.src = objectURL;
});
You can also use the Response.Response()
constructor to create your own custom Response
object:
const response = new Response();
An Ajax Call
Here we call a PHP program file that generates a JSON string, displaying the result as a JSON value, including simple error handling.
// Function to do an Ajax call
const doAjax = async () => {
const response = await fetch('Ajax.php'); // Generate the Response object
if (response.ok) {
const jsonValue = await response.json(); // Get JSON value from the response body
return Promise.resolve(jsonValue);
} else {
return Promise.reject('*** PHP file not found');
}
}
// Call the function and output value or error message to console
doAjax().then(console.log).catch(console.log);
Specifications
Specification | Status | Comment |
---|---|---|
Fetch The definition of 'Response' in that specification. |
Living Standard | Initial definition |
Browser compatibility
BCD tables only load in the browser