@fewlines-education/request

Request

• Installation
• Common Usage
  • Plain text or HTML
  • JSON
  • Simple Post
  • Post with JSON
  • Post with form parameters
  • Handling exceptions
  • Handling client and server errors
• API
  • request(url[, options], callback)
  • Options
    • Default Headers
    • Custom Agent
  • Class: Request
    • new Request(input[, options])
  • Class: Response
    • new Response([body[, options]])
    • response.ok
    • response.redirected
    • response.type
  • Class: Headers
    • new Headers([init])
  • Interface: Body
    • body.body
    • body.bodyUsed
  • Class: FetchError
• TypeScript

Installation

With Yarn:

yarn add @fewlines-education/request

With NPM:

npm install @fewlines-education/request

Common Usage

With TypeScript or using ESM:

import request from "@fewlines-education/request";

With CommonJS:

const request = require("@fewlines-education/request").default;
```

### Plain text or HTML

```js
import request from "@fewlines-education/request";

request("https://github.com/", (error, body) => {
  console.log(body);
});

JSON

import request from "@fewlines-education/request";

reqest("https://api.github.com/users/github", (error, body) => {
  const data = JSON.parse(body);
  console.log(data);
});

Simple Post

import request from "@fewlines-education/request";

request(
  "https://httpbin.org/post",
  {
    method: "POST",
    body: "a=1",
  },
  (error, body) => {
    const data = JSON.parse(body);
    console.log(data);
  }
);

Post with JSON

import request from "@fewlines-education/request";

const body = { a: 1 };

request(
  "https://httpbin.org/post",
  {
    method: "post",
    body: JSON.stringify(body),
    headers: { "Content-Type": "application/json" },
  },
  (error, body) => {
    const data = JSON.parse(body);
    console.log(data);
  }
);

Post with form parameters

URLSearchParams is available on the global object in Node.js as of v10.0.0. See official documentation 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:

import request from "@fewlines-education/request";

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

request(
  "https://httpbin.org/post",
  {
    method: "POST",
    body: params,
  },
  (error, body) => {
    const data = JSON.parse(body);
    console.log(data);
  }
);

Handling exceptions

NOTE: 3xx-5xx responses are NOT exceptions, and should be handled with the Response

import request from "@fewlines-education/request";

request("https://domain.invalid/", (error) => {
  console.log(error);
});

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:

import request from "@fewlines-education/request";

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

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

request("https://httpbin.org/status/400", (error, body, response) => {
  try {
    checkStatus(response);
  } catch (error) {
    console.error(error);
    const errorBody = await error.response.text();
    console.error(`Error body: ${errorBody}`);
  }
});

Accessing Headers and other Metadata

import request from "@fewlines-education/request";

request("https://github.com/", (error, body, response) => {
  console.log(response.ok);
  console.log(response.status);
  console.log(response.statusText);
  console.log(response.headers.raw());
  console.log(response.headers.get("content-type"));
});

API

request(url[, options], callback)

• url A string representing the URL for fetching
• options Options for the HTTP(S) request
• callback A function that will be called with:
  • error If an error occured, it will contain the error, otherwise this will be null
  • body The body of the response as a string
  • response The Response of the request

Perform an HTTP(S) fetch.

url should be an absolute URL, such as https://example.com/. A path-relative URL (/file/under/root) or protocol-relative URL (//can-be-http-or-https.com/) will result in an error.

Options

The default values are shown after each option key.

{
	// These properties are part of the Fetch Standard
	method: 'GET',
	headers: {},            // Request headers. format is the identical to that accepted by the Headers constructor (see below)
	body: null,             // Request body. can be null, or a Node.js Readable stream
	redirect: 'follow',     // Set to `manual` to extract redirect headers, `error` to reject redirect
	signal: null,           // Pass an instance of AbortSignal to optionally abort requests

	// The following properties are node-fetch extensions
	follow: 20,             // maximum redirect count. 0 to not follow redirect
	compress: true,         // support gzip/deflate content encoding. false to disable
	size: 0,                // maximum response body size in bytes. 0 to disable
	agent: null,            // http(s).Agent instance or function that returns an instance (see below)
	highWaterMark: 16384,   // the maximum number of bytes to store in the internal buffer before ceasing to read from the underlying resource.
	insecureHTTPParser: false	// Use an insecure HTTP parser that accepts invalid HTTP headers when `true`.
}

Default Headers

If no values are set, the following request headers will be sent automatically:

Header	Value
Accept-Encoding	gzip,deflate,br (when options.compress === true)
Accept	*/*
Connection	close (when no options.agent is present)
Content-Length	(automatically calculated, if possible)
Host	(host and port information from the target URI)
Transfer-Encoding	chunked (when req.body is a stream)
User-Agent	node-fetch

Note: when body is a Stream, Content-Length is not set automatically.

Custom Agent

The agent option allows you to specify networking related options which are out of the scope of Fetch, including and not limited to the following:

• Support self-signed certificate
• Use only IPv4 or IPv6
• Custom DNS Lookup

See http.Agent for more information.

In addition, the agent option accepts a function that returns http(s).Agent instance given current URL, this is useful during a redirection chain across HTTP and HTTPS protocol.

import http from "node:http";
import https from "node:https";

const httpAgent = new http.Agent({
  keepAlive: true,
});
const httpsAgent = new https.Agent({
  keepAlive: true,
});

const options = {
  agent: function (_parsedURL) {
    if (_parsedURL.protocol == "http:") {
      return httpAgent;
    } else {
      return httpsAgent;
    }
  },
};

Class: Request

An HTTP(S) request containing information about URL, method, headers, and the body. This class implements the Body interface.

Due to the nature of Node.js, the following properties are not implemented at this moment:

• type
• destination
• mode
• credentials
• cache
• integrity
• keepalive

The following extension properties are provided:

• follow
• compress
• counter
• agent
• highWaterMark

See options for exact meaning of these extensions.

new Request(input[, options])

(spec-compliant)

• input A string representing a URL, or another Request (which will be cloned)
• options [Options][#fetch-options] for the HTTP(S) request

Constructs a new Request object. The constructor is identical to that in the browser.

In most cases, directly request(url, options, callback) is simpler than creating a Request object.

Class: Response

An HTTP(S) response. This class implements the Body interface.

The following properties are not implemented at this moment:

• trailer

new Response([body[, options]])

(spec-compliant)

• body A String or [Readable stream][node-readable]
• options A [ResponseInit][response-init] options dictionary

Constructs a new Response object. The constructor is identical to that in the browser.

Because Node.js does not implement service workers (for which this class was designed), one rarely has to construct a Response directly.

response.ok

(spec-compliant)

Convenience property representing if the request ended normally. Will evaluate to true if the response status was greater than or equal to 200 but smaller than 300.

response.redirected

(spec-compliant)

Convenience property representing if the request has been redirected at least once. Will evaluate to true if the internal redirect counter is greater than 0.

response.type

(deviation from spec)

Convenience property representing the response's type. request only supports 'default' and 'error' and does not make use of filtered responses.

Class: Headers

This class allows manipulating and iterating over a set of HTTP headers. All methods specified in the [Fetch Standard][whatwg-fetch] are implemented.

new Headers([init])

(spec-compliant)

• init Optional argument to pre-fill the Headers object

Construct a new Headers object. init can be either null, a Headers object, an key-value map object or any iterable object.

// Example adapted from https://fetch.spec.whatwg.org/#example-headers-class
import { Headers } from "@fewlines-education/request";

const meta = {
  "Content-Type": "text/xml",
};
const headers = new Headers(meta);

// The above is equivalent to
const meta = [["Content-Type", "text/xml"]];
const headers = new Headers(meta);

// You can in fact use any iterable objects, like a Map or even another Headers
const meta = new Map();
meta.set("Content-Type", "text/xml");
const headers = new Headers(meta);
const copyOfHeaders = new Headers(headers);

Interface: Body

Body is an abstract interface with methods that are applicable to both Request and Response classes.

body.body

(deviation from spec)

• Node.js [Readable stream][node-readable]

Data are encapsulated in the Body object. Note that while the [Fetch Standard][whatwg-fetch] requires the property to always be a WHATWG ReadableStream, in request it is a Node.js [Readable stream][node-readable].

body.bodyUsed

(spec-compliant)

• Boolean

A boolean property for if this body has been consumed. Per the specs, a consumed body cannot be used again.

Class: FetchError

(node-fetch extension)

An operational error in the fetching process.

TypeScript

types are bundled with @fewlines-education/request, so you don't need to install any additional packages.