Logging and middleware

Customize the fetch function to inspect and modify requests and responses

You can provide a custom fetch function when instantiating the client, which can be used to inspect or alter the Request or Response before/after each request.

Custom fetch function

Provide a custom fetch implementation to intercept all HTTP requests:

import { fetch } from 'undici'; // as one example
import Cloudflare from 'cloudflare';

const client = new Cloudflare({
  fetch: async (url: RequestInfo, init?: RequestInit): Promise<Response> => {
    console.log('About to make a request', url, init);
    const response = await fetch(url, init);
    console.log('Got response', response);
    return response;
  },
});

This approach is useful for logging, request signing, response transformation, or integrating with custom HTTP clients.

Logging requests and responses

You can use the custom fetch function to log all API interactions:

import Cloudflare from 'cloudflare';

const client = new Cloudflare({
  fetch: async (url: RequestInfo, init?: RequestInit): Promise<Response> => {
    const startTime = Date.now();
    console.log(`[${new Date().toISOString()}] ${init?.method || 'GET'} ${url}`);
    
    const response = await fetch(url, init);
    const duration = Date.now() - startTime;
    
    console.log(`[${new Date().toISOString()}] ${response.status} ${url} (${duration}ms)`);
    return response;
  },
});

Debug mode

If you set a DEBUG=true environment variable, this library will log all requests and responses automatically:

DEBUG=true node your-script.js

Debug mode is intended for debugging purposes only and may change in the future without notice.

Request and response inspection

Use the custom fetch function to inspect headers, modify requests, or handle responses:

import Cloudflare from 'cloudflare';

const client = new Cloudflare({
  fetch: async (url: RequestInfo, init?: RequestInit): Promise<Response> => {
    // Inspect request headers
    console.log('Request headers:', init?.headers);
    
    // Make the request
    const response = await fetch(url, init);
    
    // Inspect response headers
    console.log('Response headers:', Object.fromEntries(response.headers.entries()));
    console.log('Rate limit remaining:', response.headers.get('x-ratelimit-remaining'));
    
    return response;
  },
});

Using alternative fetch implementations

By default, this library uses node-fetch in Node, and expects a global fetch function in other environments.

If you would prefer to use a global, web-standards-compliant fetch function even in a Node environment (for example, if you are running Node with --experimental-fetch or using NextJS which polyfills with undici), add the following import before your first import from "cloudflare":

// Tell TypeScript and the package to use the global web fetch instead of node-fetch.
// Note, despite the name, this does not add any polyfills, but expects them to be provided if needed.
import 'cloudflare/shims/web';
import Cloudflare from 'cloudflare';

To do the inverse, add import "cloudflare/shims/node" (which does import polyfills).

This can also be useful if you are getting the wrong TypeScript types for Response.