Skip to content
A JavaScript Fetch API mixin to throw FetchError when the request fails or response has an error.
JavaScript Makefile
Branch: master
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Permalink
Type Name Latest commit message Commit time
Failed to load latest commit information.
test
.editorconfig
.gitignore
.npmignore
.travis.yml
CHANGELOG.md
LICENSE
Makefile
README.md
index.js
package.json

README.md

FetchThrow.js

NPM version Build status

FetchThrow.js is a mixin for the Fetch API for browsers and Node.js that rejects the returned promise with a FetchError.js instance should the network request fail or the response have a status of at least 400 and less than 600 (as defined for error responses in the HTTP specs).

Installing

npm install fetch-throw

FetchThrow.js follows semantic versioning, so feel free to depend on its major version with something like >= 1.0.0 < 2 (a.k.a ^1.0.0).

If you'd like more convenient access to the thrown FetchError instance (e.g. for instanceof checks), also install fetch-error and ensure there's only one installed:

npm install fetch-error
npm dedupe fetch-error

Using

Wrap the native fetch function with the one from FetchThrow.js:

var fetch = require("fetch-throw")(global.fetch)

Then call the returned function as you would with the regular Fetch API:

var res = fetch("/models/42")

Should /models respond with 404, res will be rejected with an instance of FetchError. The FetchError property on FetchThrow is identical to doing require("fetch-error").

var FetchError = require("fetch-throw").FetchError

res.catch(function(err) {
  if (err instanceof FetchError) {
    var req = err.request
    console.error("%s %s failed: %s", req.method, req.url, err.message)
  }

  throw err
})

In case of unexpected errors (such as network name lookup failures) thrown by fetch before a request is made, res will also be rejected with an instance of FetchError. This allows you to identify failed requests for logging, for example, as shown above.

For a description of properties on the error, see below.

Browser

Browsers have the Fetch API available at window.fetch:

var fetch = require("fetch-throw")(window.fetch)
fetch("/models/42")

Node.js

Node.js doesn't have a built-in implementation of the Fetch API, but you can use any library with a compatible interface, such as my Fetch/Off.js or node-fetch:

var fetch = require("fetch-throw")(require("node-fetch"))
fetch("/models/42")

Properties on an instance of FetchError

Property Description
code Response's statusCode or 0 in case of network error.
message Response's statusText or "Network Error.".
request A new Fetch API Request object to help identify the request.
response The Fetch API Response of the failed request.
error In case of non-response errors, it's set to the original error.

License

FetchThrow.js is released under a Lesser GNU Affero General Public License, which in summary means:

  • You can use this program for no cost.
  • You can use this program for both personal and commercial reasons.
  • You do not have to share your own program's code which uses this program.
  • You have to share modifications (e.g. bug-fixes) you've made to this program.

For more convoluted language, see the LICENSE file.

About

Andri Möll typed this and the code.
Monday Calendar supported the engineering work.

If you find FetchThrow.js needs improving, please don't hesitate to type to me now at andri@dot.ee or create an issue online.

You can’t perform that action at this time.