Request() - Web APIs 编辑

The Request() constructor creates a new Request object.

Syntax

var myRequest = new Request(input[, init]);

Parameters

input

Defines the resource that you wish to fetch. This can either be:

• A USVString containing the direct URL of the resource you want to fetch.
• A Request object, effectively creating a copy. Note the following behavioural 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 of navigate, the mode value is converted to same-origin.

init Optional

An options object containing any custom settings that you want to apply to the request. The possible options are:

• method: The request method, e.g., GET, POST. The default is GET.
• headers: Any headers you want to add to your request, contained within a Headers object or an object literal with ByteString values.
• body: Any body that you want to add to your request: this can be a Blob, BufferSource, FormData, URLSearchParams, USVString, or ReadableStream object. Note that a request using the GET or HEAD method cannot have a body.
• mode: The mode you want to use for the request, e.g., cors, no-cors, same-origin, or navigate. The default is cors.
• credentials: The request credentials you want to use for the request: omit, same-origin, or include. The default is same-origin.
• cache: The cache mode you want to use for the request.
• redirect: The redirect mode to use: follow, error, or manual. The default is follow.
• referrer: A USVString specifying no-referrer, client, or a URL. The default is about:client.
• integrity: Contains the subresource integrity value of the request (e.g., sha256-BpfBw7ivV8q2jLiT13fxDYAe2tJllusRSZ273h2nFSE=).

Errors

Example

In our Fetch Request example (see Fetch Request live) we create a new Request object using the constructor, then fetch it using a GlobalFetch.fetch call. Since we are fetching an image, we run Body.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.

var myImage = document.querySelector('img');

var myRequest = new Request('flowers.jpg');

fetch(myRequest).then(function(response) {
  return response.blob();
}).then(function(response) {
  var 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 init object when we invoke fetch():

var myImage = document.querySelector('img');

var myHeaders = new Headers();
myHeaders.append('Content-Type', 'image/jpeg');

var myInit = { method: 'GET',
               headers: myHeaders,
               mode: 'cors',
               cache: 'default' };

var myRequest = new Request('flowers.jpg',myInit);

fetch(myRequest).then(function(response) {
  ...
});

Note that you could also pass the init object into the fetch call to get the same effect, e.g.:

fetch(myRequest,myInit).then(function(response) {
  ...
});

You can also use an object literal as headers in init.

var myInit = { method: 'GET',
               headers: {
                   'Content-Type': 'image/jpeg'
               },
               mode: 'cors',
               cache: 'default' };

var myRequest = new Request('flowers.jpg', myInit);

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.)

var copy = new Request(myRequest);

Note: This last usage is probably only useful in ServiceWorkers.

Specifications

Browser compatibility

BCD tables only load in the browser

See also

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