fetch-dedupe

library3.0.0jsnpmunverified

A lightweight, fetch-compatible HTTP client (v3.0.0) that transparently deduplicates identical in-flight requests and caches responses to improve performance in complex web apps. Unlike raw fetch, it groups concurrent requests with the same URL, method, and body into a single network call, and can cache responses for subsequent requests. It exports a fetchDedupe function, cache management utilities, and error types. Works in browsers and Node 18+ with global fetch.

devops

npm install fetch-dedupe

github ↗package ↗homepage ↗

INSTALL

IMPORT

SIG · FETCH-DEDUPE

fetch-dedupe

devopsjavascriptv3.0.0

harness data pending

Install & Compatibility

Where this runs

No compatibility data collected yet for this library.

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

fetchDedupe

✓ import { fetchDedupe } from 'fetch-dedupe'

✗ import fetchDedupe from 'fetch-dedupe'

This library exports named exports only. Default import will yield undefined.

responseCache

✓ import { responseCache } from 'fetch-dedupe'

✗ const { responseCache } = require('fetch-dedupe')

If using CommonJS in Node < 18, use const { fetchDedupe, responseCache } = require('fetch-dedupe').

activeRequests

✓ import { activeRequests } from 'fetch-dedupe'

✗ import { activeRequests } from 'fetch-dedupe/activeRequests'

All exports are at the package root; there are no subpath exports.

CacheMissError

✓ import { CacheMissError } from 'fetch-dedupe'

Error class for cache misses when using responseCache.get().

Shows how to use fetchDedupe as a drop-in fetch replacement that dedupes concurrent requests.

import { fetchDedupe } from 'fetch-dedupe'; async function demo() { const data = await fetchDedupe('/api/data'); console.log('Response:', data); } demo();

Debug

Known issues

breakingv3 drops Node < 18 support and requires a global fetch implementation (e.g., Node 18+ or a polyfill).

fix

Upgrade to Node 18 or later, or use a fetch polyfill like undici or node-fetch.

affects: >=3.0.0

breakingv3 removes the ability to pass a plain string URL as first argument without options? Actually, still supported. Check documentation.

fix

URL as first argument still works; no change needed.

affects: >=3.0.0

deprecatedThe `responseType` option as a string is deprecated. Use `responseType` as a function in v3.

fix

Pass a function: responseType: (res) => res.status === 204 ? 'text' : 'json'

affects: >=3.0.0

gotchaThe `responseCache` is a global, shared cache. If you need per-request caching, manage your own cache.

fix

Use responseCache.clear() between tests or create isolated contexts.

affects: >=0.0.0

gotchaThe `requestKey` option defaults to URL + method + body. If you mutate the body (e.g., JSON.stringify), two identical requests may not dedupe if body order differs.

fix

Pass a custom requestKey to normalize body ordering.

affects: >=0.0.0

gotchaThe library does not handle fetch errors (network failures) – those rejections are passed through as-is.

fix

Always add a .catch() or try/catch around fetchDedupe.

affects: >=0.0.0

Errors

Common errors & fixes

TypeError: fetchDedupe is not a function

Using default import instead of named import.

fix

Change to: import { fetchDedupe } from 'fetch-dedupe';

window.fetch is not a function

Using fetch-dedupe in an environment without a global fetch (e.g., older Node).

fix

Install a fetch polyfill and set globalThis.fetch = require('node-fetch');

UnhandledPromiseRejection: TypeError: Failed to fetch

Network error or CORS issue; fetch-dedupe does not wrap fetch errors.

fix

Add a catch block: fetchDedupe('/api').catch(err => console.error(err));

Cannot read properties of undefined (reading 'json')

Response type parsing failed; often because response body is empty or wrong content-type.

fix

Set responseType explicitly or handle non-JSON responses with a function.

Upgrade

Version history

3.0.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/jmeas/fetch-dedupe ↗

packagefetch-dedupe ↗

homepagehttps://github.com/jmeas/fetch-dedupe#readme ↗