Fetch utilities

import { forceFetchAsXHR, fetch, Headers, Request, Response, DOMException } from '@bbc/front-end-kit/js/utils/fetch';

This file contains the ability to launch a polyfill for the browser's Fetch API on demand. The kit provides this mainly for Showpad projects so they can run on Android without conflicting with the securities of the File protocol, which blocks Fetch API functionalities. XHR is still available. Thanks to this utility, we are able to run our Showpad experiences using modern JavaScript without the need to refactor the codebase for Android.

forceFetchAsXHR(condition, logMessage)

Forces the Fetch API to use XHR under the hood by replacing window.fetch with the bundled XHR-backed polyfill — even when the browser already supports native fetch. Useful for Showpad Android environments where the File protocol blocks native fetch.

Parameters

• condition (boolean, default true): Only applies the override when truthy. Useful for targeting specific environments.
• logMessage (string, optional): Message logged to the console on activation. Defaults to a generic override notification.

Returns

undefined

import { forceFetchAsXHR } from '@bbc/front-end-kit/js/utils/fetch';

// always override
forceFetchAsXHR();

// only override on Android
forceFetchAsXHR(
    navigator.userAgent.toLowerCase().includes('android'),
    'Fetch API override activated: Android detected'
);

fetch(input, init)

The XHR-backed fetch implementation (a modified port of github/fetch). Has the same signature as the native Fetch API. Used internally by forceFetchAsXHR and installed globally when native fetch is absent.

Headers

Fetch-compatible Headers constructor. Supports append, delete, get, has, set, forEach, keys, values, entries.

Request

Fetch-compatible Request constructor. Must be called with new. Supports clone().

Response

Fetch-compatible Response constructor. Must be called with new. Supports clone(), Response.error(), Response.redirect(url, status).

DOMException

Re-export of the global DOMException, with a polyfill fallback for environments where it is unavailable.