Parsing Dates

Dates in feeds are notoriously unreliable — wrong formats, missing timezones, localized strings, inconsistencies within the same feed. Rather than shipping a built-in parser that handles some cases and silently fails on others, Feedsmith returns date strings as-is and lets you bring your own parsing logic via the parseDateFn option. This way you can use whichever date library (or the native Date constructor) fits your needs and handle edge cases on your terms.

The function receives the raw (trimmed) date string and its return value replaces it in the result.

Using Date constructor

import { parseFeed } from 'feedsmith'

const { feed } = parseFeed(xml, {
  parseDateFn: (raw) => new Date(raw),
})

feed.pubDate // Date

Using a date library

import { parseRssFeed } from 'feedsmith'
import { parse } from 'date-fns'

const feed = parseRssFeed(xml, {
  parseDateFn: (raw) => {
    return parse(raw, 'EEE, dd MMM yyyy HH:mm:ss xx', new Date())
  },
})

feed.pubDate // Date

Type safety with TDate

All parse functions accept a generic TDate parameter that defaults to string. When parseDateFn is provided, TDate is inferred from its return type, so all date fields in the result are typed accordingly:

import { parseAtomFeed } from 'feedsmith'

// Without parseDateFn — dates are strings.
const feed = parseAtomFeed(xml)
feed.updated // string | undefined

// With parseDateFn — dates match the return type.
const feed = parseAtomFeed(xml, {
  parseDateFn: (raw) => new Date(raw),
})
feed.updated // Date | undefined

Error handling

Errors thrown by parseDateFn are not caught — they propagate to the caller. You should wrap your logic in a try/catch if it might throw. This is intentional — silently swallowing errors would hide invalid dates, and you're better off deciding how to handle them yourself.

If a date string is empty or whitespace-only, parseDateFn is not called and the field is omitted from the result.