ERROR-HANDLING.md

Error handling with node-fetch

Because window.fetch isn't designed to be transparent about the cause of request errors, we have to come up with our own solutions.

The basics:

• A cancelled request is rejected with an AbortError. You can check if the reason for rejection was that the request was aborted by checking the Error's name is AbortError.

const fetch = require('node-fetch');

(async () => {
	try {
		await fetch(url, {signal});
	} catch (error) {
		if (error.name === 'AbortError') {
			console.log('request was aborted');
		}
	}
})();

• All operational errors other than aborted requests are rejected with a FetchError. You can handle them all through the try/catch block or promise catch clause.

• All errors come with an error.message detailing the cause of errors.

• All errors originating from node-fetch are marked with a custom err.type.

• All errors originating from Node.js core are marked with error.type = 'system', and in addition contain an error.code and an error.errno for error handling. These are aliases for error codes thrown by Node.js core.

• Programmer errors are either thrown as soon as possible, or rejected with default Error with error.message for ease of troubleshooting.

List of error types:

• Because we maintain 100% coverage, see test/main.js for a full list of custom FetchError types, as well as some of the common errors from Node.js