How to use node-fetch-npm - 6 common examples

function cachingFetch (uri, _opts) {
  const opts = configureOptions(_opts)

  if (opts.integrity) {
    initializeSsri()
    // if verifying integrity, node-fetch must not decompress
    opts.compress = false
  }

  const isCachable = (opts.method === 'GET' || opts.method === 'HEAD') &&
    opts.cacheManager &&
    opts.cache !== 'no-store' &&
    opts.cache !== 'reload'

  if (isCachable) {
    const req = new fetch.Request(uri, {
      method: opts.method,
      headers: opts.headers
    })

    return opts.cacheManager.match(req, opts).then(res => {
      if (res) {
        const warningCode = (res.headers.get('Warning') || '').match(/^\d+/)
        if (warningCode && +warningCode >= 100 && +warningCode < 200) {
          // https://tools.ietf.org/html/rfc7234#section-4.3.4
          //
          // If a stored response is selected for update, the cache MUST:
          //
          // * delete any Warning header fields in the stored response with
          //   warn-code 1xx (see Section 5.5);
          //
          // * retain any Warning header fields in the stored response with

!isStream && (
              res.status === 408 || // Request Timeout
              res.status === 420 || // Enhance Your Calm (usually Twitter rate-limit)
              res.status === 429 || // Too Many Requests ("standard" rate-limiting)
              res.status >= 500 // Assume server errors are momentary hiccups
            )

          if (isRetriable) {
            if (typeof opts.onRetry === 'function') {
              opts.onRetry(res)
            }

            return retryHandler(res)
          }

          if (!fetch.isRedirect(res.status) || opts.redirect === 'manual') {
            return res
          }

          // handle redirects - matches behavior of npm-fetch: https://github.com/bitinn/node-fetch
          if (opts.redirect === 'error') {
            const err = new Error(`redirect mode is set to error: ${uri}`)
            err.code = 'ENOREDIRECT'
            throw err
          }

          if (!res.headers.get('location')) {
            const err = new Error(`redirect location header missing at: ${uri}`)
            err.code = 'EINVALIDREDIRECT'
            throw err
          }

function remoteFetch (uri, opts) {
  const agent = getAgent(uri, opts)
  const headers = Object.assign({
    'connection': agent ? 'keep-alive' : 'close',
    'user-agent': USER_AGENT
  }, opts.headers || {})

  const reqOpts = {
    agent,
    body: opts.body,
    compress: opts.compress,
    follow: opts.follow,
    headers: new fetch.Headers(headers),
    method: opts.method,
    redirect: 'manual',
    size: opts.size,
    counter: opts.counter,
    timeout: opts.timeout
  }

  return retry(
    (retryHandler, attemptNum) => {
      const req = new fetch.Request(uri, reqOpts)
      return fetch(req)
        .then(res => {
          res.headers.set('x-fetch-attempts', attemptNum)

          if (opts.integrity) {
            remoteFetchHandleIntegrity(res, opts.integrity)

.then(newRes => {
            newRes.headers = new fetch.Headers(revalidatedPolicy.policy.responseHeaders())
            return newRes
          })
      }

(retryHandler, attemptNum) => {
      const req = new fetch.Request(uri, reqOpts)
      return fetch(req)
        .then(res => {
          res.headers.set('x-fetch-attempts', attemptNum)

          if (opts.integrity) {
            remoteFetchHandleIntegrity(res, opts.integrity)
          }

          const isStream = req.body instanceof Stream

          if (opts.cacheManager) {
            const isMethodGetHead = req.method === 'GET' ||
              req.method === 'HEAD'

            const isCachable = opts.cache !== 'no-store' &&
              isMethodGetHead &&

function cacheDelete (uri, opts) {
  opts = configureOptions(opts)
  if (opts.cacheManager) {
    const req = new fetch.Request(uri, {
      method: opts.method,
      headers: opts.headers
    })
    return opts.cacheManager.delete(req, opts)
  }
}