Request: Request() constructor
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since March 2017.
Note: This feature is available in Web Workers.
The Request()
constructor creates a new
Request
object.
Syntax
new Request(input)
new Request(input, options)
Parameters
input
-
Defines the resource that you wish to fetch. This can either be:
-
A string containing the URL of the resource you want to fetch. The URL may be relative to the base URL, which is the document's
baseURI
in a window context, orWorkerGlobalScope.location
in a worker context. -
A
Request
object, effectively creating a copy. Note the following behavioral updates to retain security while making the constructor less likely to throw exceptions:-
If this object exists on another origin to the constructor call, the
Request.referrer
is stripped out. -
If this object has a
Request.mode
ofnavigate
, themode
value is converted tosame-origin
.
-
If this object exists on another origin to the constructor call, the
-
options
Optional-
A
RequestInit
object containing any custom settings that you want to apply to the request.If you construct a new
Request
from an existingRequest
, any options you set in an options argument for the new request replace any corresponding options set in the originalRequest
. For example:jsconst oldRequest = new Request( "https://github.com/mdn/content/issues/12959", { headers: { From: "webmaster@example.org" } }, ); oldRequest.headers.get("From"); // "webmaster@example.org" const newRequest = new Request(oldRequest, { headers: { From: "developer@example.org" }, }); newRequest.headers.get("From"); // "developer@example.org"
Exceptions
Type | Description |
---|---|
TypeError |
Since Firefox 43,
Request() will throw a TypeError if the URL has
credentials, such as http://user:password@example.com.
|
Examples
In our Fetch Request example (see Fetch Request live) we
create a new Request
object using the constructor, then fetch it using a
fetch()
call. Since we are fetching an image, we run
Response.blob
on the response to give it the proper MIME type so it will be
handled properly, then create an Object URL of it and display it in an
<img>
element.
const myImage = document.querySelector("img");
const myRequest = new Request("flowers.jpg");
fetch(myRequest)
.then((response) => response.blob())
.then((response) => {
const objectURL = URL.createObjectURL(response);
myImage.src = objectURL;
});
In our Fetch Request with init example (see Fetch Request init live) we do the same thing except that we pass in an options object when we invoke fetch()
.
In this case, we can set a Cache-Control
value to indicate what kind of cached responses we're okay with:
const myImage = document.querySelector("img");
const reqHeaders = new Headers();
// A cached response is okay unless it's more than a week old.
reqHeaders.set("Cache-Control", "max-age=604800");
const options = {
headers: reqHeaders,
};
// pass init as an "options" object with our headers
const req = new Request("flowers.jpg", options);
fetch(req).then((response) => {
// ...
});
Note that you could also pass options
into the fetch
call to get the same effect, e.g.:
fetch(req, options).then((response) => {
// ...
});
You can also use an object literal as headers
in options
.
const options = {
headers: {
"Cache-Control": "max-age=60480",
},
};
const req = new Request("flowers.jpg", options);
You may also pass a Request
object to the Request()
constructor to create a copy of the Request (This is similar to calling the
clone()
method.)
const copy = new Request(req);
Note: This last usage is probably only useful in ServiceWorkers.
Specifications
Specification |
---|
Fetch Standard # ref-for-dom-request① |
Browser compatibility
BCD tables only load in the browser