Registry / http-networking / fetch-intercept

fetch-intercept

library2.4.0jsnpmunverified

A lightweight library to intercept and modify fetch requests and responses, inspired by Angular HTTP interceptors. Version 2.4.0 is the latest stable release, with infrequent updates. It monkey-patches the global fetch function to allow addition of request/response interceptors in browser, Node, and WebWorker environments. Unlike other interceptors, it uses a simple register/unregister pattern and supports TypeScript definitions, making it easy to add logging, authentication headers, or error handling without modifying fetch calls directly. It requires fetch to be available (polyfill suggested for older environments).

http-networking web-framework

npm install fetch-intercept

github ↗package ↗

INSTALL

IMPORT

SIG · FETCH-INTERCEPT

fetch-intercept

http-networkingjavascriptv2.4.0

Install

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Import

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Disk

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Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

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

default

✓ import fetchIntercept from 'fetch-intercept';

✗ import { fetchIntercept } from 'fetch-intercept';

The package exports a default object, not named exports. Use default import.

✓ import fetchIntercept from 'fetch-intercept'; const unregister = fetchIntercept.register({...});

✗ import { register } from 'fetch-intercept';

unregister

✓ import fetchIntercept from 'fetch-intercept'; const unregister = fetchIntercept.register({...}); unregister();

✗ import { unregister } from 'fetch-intercept';

unregister is a function returned by register(), not a named export.

Demonstrates registering interceptors to modify fetch requests and responses, then unregistering.

import fetchIntercept from 'fetch-intercept'; // Register interceptors const unregister = fetchIntercept.register({ request: function (url, config) { // Modify the request: add headers const newConfig = { ...config, headers: { ...config?.headers, 'X-Interceptor': 'true' } }; return [url, newConfig]; }, response: function (response) { // Modify the response: log status console.log('Response status:', response.status); return response; }, }); // Use fetch normally fetch('https://jsonplaceholder.typicode.com/todos/1') .then(response => response.json()) .then(data => console.log(data)) .finally(() => unregister()); // Clean up export {}; // Ensure module context for TypeScript

Debug

Known issues

gotchafetch-intercept modifies the global fetch. Calling register() multiple times stacks interceptors; unregister() removes the last registered interceptor.

fix

Keep track of unregister functions and call them in reverse order to fully clean up.

affects: >=1.0

gotchaThe request interceptor must return an array of [url, config] or undefined to retain original. Returning null or other types may break fetch.

fix

Always return [url, config] from request interceptor, even if unchanged.

affects: >=1.0

gotchafetch-intercept does not work with AbortController in older versions; abort signals may be lost in interceptors.

fix

Upgrade to version 2.x for better AbortController support, or manually handle signal in config.

affects: <2.0

deprecatedThe library has not been updated for several years; future browser fetch changes may break compatibility.

fix

Consider alternative interceptors like 'undici' or custom wrappers if active maintenance is required.

affects: all

Errors

Common errors & fixes

TypeError: Failed to fetch

Interceptor does not return proper [url, config] array or returns undefined.

fix

Ensure request interceptor returns a tuple: return [url, config];

fetchInterceptor.register is not a function

Incorrect import syntax (e.g., named import instead of default).

fix

Use default import: import fetchIntercept from 'fetch-intercept';

Cannot read properties of undefined (reading 'headers')

Config object is undefined when no options are passed to fetch.

fix

Use optional chaining: config?.headers, or provide default empty object: const newConfig = config || {};

Upgrade

Version history

2.4.0latest on npm

Audit

Dependencies

No dependency data recorded yet.

Agent activity

14 hits · last 30 days

node

Resources

githubhttps://github.com/werk85/fetch-intercept ↗

packagehttps://www.npmjs.com/package/fetch-intercept ↗