@humanwhocodes/guarded-fetch

Guarded Fetch

by Nicholas C. Zakas

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Description

A wrapper around fetch() that catches errors and returns them in a consistent format. Instead of using try-catch blocks, you can use guardedFetch() which always returns an object with response and error properties.

Installation

npm install @humanwhocodes/guarded-fetch

Usage

Using guardedFetch (with global fetch)

The guardedFetch function is a wrapped version of the global fetch() function:

import { guardedFetch } from "@humanwhocodes/guarded-fetch";

// Successful request
const { response, error } = await guardedFetch("https://api.example.com/data");
if (error) {
	console.error("Fetch failed:", error);
} else {
	console.log("Response:", response);
}

// Failed request (network error)
const { response: response2, error: error2 } = await guardedFetch("https://invalid-domain.example");
if (error2) {
	console.error("Fetch failed:", error2); // Error will be defined
}

// HTTP error (like 404)
const { response: response3, error: error3 } = await guardedFetch("https://api.example.com/not-found");
if (error3) {
	console.error("Fetch failed:", error3);
} else if (!response3.ok) {
	console.log("HTTP error:", response3.status);
}

Using createGuardedFetch (with custom fetch)

You can wrap any fetch() implementation using createGuardedFetch():

import { createGuardedFetch } from "@humanwhocodes/guarded-fetch";
import nodeFetch from "node-fetch";

const guardedNodeFetch = createGuardedFetch(nodeFetch);

const { response, error } = await guardedNodeFetch("https://api.example.com/data");
if (error) {
	console.error("Fetch failed:", error);
} else {
	console.log("Response:", response);
}

Return Value

Both guardedFetch() and the function returned by createGuardedFetch() return a promise that resolves to an object with the following properties:

• response - The Response object if the fetch was successful, or undefined if an error occurred
• error - Any error thrown by fetch() (type: any), or undefined if the fetch was successful

Note: HTTP errors (like 404 or 500) are NOT treated as errors by fetch(). You need to check response.ok or response.status to handle HTTP errors.

License

Copyright 2025 Nicholas C. Zakas

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.