Feedscout

discoverHubs ​

Discovers WebSub hubs from a feed or webpage.

Signature ​

typescript
function discoverHubs(
  input: DiscoverInput,
  options?: DiscoverHubsOptions,
): Promise<Array<HubResult>>

Parameters ​

input ​

The URL to discover hubs from. Can be a string or an object:

typescript
// String - URL to fetch and scan
discoverHubs('https://example.com/feed.xml')

// Object - provide existing content/headers
discoverHubs({
  url: 'https://example.com/feed.xml',
  content: feedContent,
  headers: responseHeaders,
})

options ​

PropertyTypeDefaultDescription
methodsDiscoverHubsMethodsConfigallMethods to use
fetchFnFetchFnnative fetchCustom fetch function
resolveUrlFnDiscoverResolveUrlFnresolve relativeCustom URL resolution
onErrorDiscoverOnErrorFnCalled when fetching the input fails or resolveUrlFn throws

methods ​

Array of discovery methods to use:

typescript
type DiscoverHubsMethodsConfig = Array<'headers' | 'html' | 'feed'>
  • headers: Parse HTTP Link headers for rel="hub".
  • feed: Extract hub links from feed content (Atom, RSS, JSON Feed).
  • html: Scan for <link rel="hub"> elements.

Return Value ​

Returns a promise that resolves to an array of hub results:

typescript
type HubResult = {
  hub: string   // Hub URL to subscribe to
  topic: string // Feed URL the hub serves updates for
}

Example result:

typescript
{
  hub: 'https://pubsubhubbub.appspot.com/',
  topic: 'https://example.com/feed.xml',
}

Examples ​

Basic Usage ​

typescript
import { discoverHubs } from 'feedscout'

const hubs = await discoverHubs('https://example.com/feed.xml')

With Specific Methods ​

typescript
const hubs = await discoverHubs('https://example.com/feed.xml', {
  methods: ['headers', 'feed'],
})

With Existing Content ​

typescript
const response = await fetch('https://example.com/feed.xml')
const content = await response.text()

const hubs = await discoverHubs(
  {
    url: 'https://example.com/feed.xml',
    content,
    headers: response.headers,
  },
  {
    methods: ['headers', 'feed'],
  },
)

With Custom HTTP Client ​

typescript
import type { FetchFn } from 'feedscout'

const myCustomFetch: FetchFn = async (url, options) => {
  const response = await fetch(url, options)

  return {
    headers: response.headers,
    body: await response.text(),
    url: response.url,
    status: response.status,
  }
}

const hubs = await discoverHubs('https://example.com/feed.xml', {
  methods: ['headers', 'feed'],
  fetchFn: myCustomFetch,
})

See Customize Data Fetching for examples with Axios, Got, Ky, and more.

With Custom URL Resolution ​

typescript
import type { DiscoverResolveUrlFn } from 'feedscout'

const resolveUrl: DiscoverResolveUrlFn = (url, baseUrl) => {
  const resolved = new URL(url, baseUrl)
  resolved.protocol = 'https:'
  return resolved.href
}

const hubs = await discoverHubs('https://example.com/feed.xml', {
  resolveUrlFn: resolveUrl,
})

See Customize URL Resolution for more examples.