Rovel Docs

# Fetch

A plugin to fetch, just like window.fetch!

# Features

  • Stay consistent with window.fetch API.
  • Make conscious trade-off when following [WHATWG fetch spec][whatwg-fetch] and stream spec (opens new window) implementation details, document known differences.
  • Use native promise and async functions.
  • Use native Node streams for body, on both request and response.
  • Decode content encoding (gzip/deflate/brotli) properly, and convert string output (such as res.text() and res.json()) to UTF-8 automatically.
  • Useful extensions such as redirect limit, response size limit, [explicit errors][error-handling.md] for troubleshooting.

# Loading and configuring the module

const fetch = require('rovel.js').fetch;

  
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If you want to patch the global object in node:

const fetch = require('rovel.js').fetch;

if (!globalThis.fetch) {
	globalThis.fetch = fetch;
}

  
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# Usage

# Get content as:

# Plain text or HTML

const fetch = require('rovel.js').fetch;

const response = await fetch('https://github.com/');
const body = await response.text();

console.log(body);

  
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# JSON

const fetch = require("rovel.js").fetch;

const response = await fetch('https://api.github.com/users/github');
const json = await response.json();

console.log(json);

  
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# Simple Post

const fetch = require("rovel.js").fetch;

const response = await fetch('https://httpbin.org/post', {method: 'POST', body: 'a=1'});
const json = await response.json();

console.log(json);

  
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# Post with JSON

const fetch = require("rovel.js").fetch;

const body = {a: 1};

const response = await fetch('https://httpbin.org/post', {
	method: 'post',
	body: JSON.stringify(body),
	headers: {'Content-Type': 'application/json'}
});
const json = await response.json();

console.log(json);

  
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# Post with form parameters

URLSearchParams is available on the global object in Node.js as of v10.0.0. See official documentation (opens new window) for more usage methods.

NOTE: The Content-Type header is only set automatically to x-www-form-urlencoded when an instance of URLSearchParams is given as such:

const fetch = require("rovel.js").fetch;

const params = new URLSearchParams();
params.append('a', 1);

const response = await fetch('https://httpbin.org/post', {method: 'POST', body: params});
const json = await response.json();

console.log(json);

  
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# Handling exceptions

NOTE: 3xx-5xx responses are NOT exceptions, and should be handled in then(), see the next section.

Wrapping the fetch function into a try/catch block will catch all exceptions, such as errors originating from node core libraries, like network errors, and operational errors which are instances of FetchError. See the [error handling document][error-handling.md] for more details.

const fetch = require("rovel.js").fetch;

try {
	await fetch('https://domain.invalid/');
} catch (error) {
	console.log(error);
}

  
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# Handling client and server errors

It is common to create a helper function to check that the response contains no client (4xx) or server (5xx) error responses:

const fetch = require("rovel.js").fetch;

class HTTPResponseError extends Error {
	constructor(response, ...args) {
		this.response = response;
		super(`HTTP Error Response: ${res.status} ${res.statusText}`, ...args);
	}
}

const checkStatus = response => {
	if (response.ok) {
		// response.status >= 200 && response.status < 300
		return res;
	} else {
		throw new HTTPResponseError(response);
	}
}

const response = await fetch('https://httpbin.org/status/400');

try {
	checkStatus(response);
} catch (error) {
	console.error(error);

	const errorBody = await error.response.text();
	console.error(`Error body: ${errorBody}`);
}

  
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# Handling cookies

Cookies are not stored by default. However, cookies can be extracted and passed by manipulating request and response headers. See Extract Set-Cookie Header for details.

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