🚨 No longer maintained. Moved to @reallyland/node_mod. 🚨

Fetch API in Node.js with specific response type

• Pre-requisites
• Install
• Usage
  • TypeScript or ES modules
  • Node.js
• @types/node-fetch for TypeScript users
• API Reference
  • FetchAsInfo
  • FetchAsReturnType
  • fetchAs
  • fetchAsArrayBuffer(url[, options])
  • fetchAsBlob(url[, options])
  • fetchAsBuffer(url[, options])
  • fetchAsJson(url[, options])
  • fetchAsText(url[, options])
  • fetchAsTextConverted(url[, options])
• License

• Node.js >= 8.9.0
• NPM >= 5.5.1 (NPM comes with Node.js so there is no need to install separately.)

# Install via NPM
$ npm install --save fetch-as

/**
 * NOTE: Additional typings file from `node-fetch` is required
 * if user decides to create their own `options` and it is based on
 * `RequestInit` from `@types/node-fetch`.
 * 
 * Run the following command to install the additional typings:-
 * 
 * $ npm install --dev @types/node-fetch
 */
import { RequestInit } from 'node-fetch';

import fetchAs from 'fetch-as';
// OR import each method explicitly
// import {
//   fetchAsArrayBuffer,
//   fetchAsBlob,
//   fetchAsBuffer,
//   fetchAsJson,
//   fetchAsText,
//   fetchAsTextConverted,
// } from 'fetch-as';

async function runFetch() {
  const opts: RequestInit = {
    method: 'GET',
  };
  const url = 'http://www.mocky.io/v2/5a50cfa82f000085158d5315';
  const jsonData = await fetchAs.json(url, opts); // OR fetchAsJson(url);

  console.log('# json', jsonData.data);
  // {
  //   "status": 200,
  //   "message": "OK",
  //   "by": "fetch-as"
  // }
}

runFetch();

const { fetchAs } = require('fetch-as');
// OR require each method explicitly
// const {
//   fetchAsArrayBuffer,
//   fetchAsBlob,
//   fetchAsBuffer,
//   fetchAsJson,
//   fetchAsText,
//   fetchAsTextConverted,
// } = require('fetch-as');

async function runFetch() {
  const url = 'http://www.mocky.io/v2/5a50cfa82f000085158d5315';
  const jsonData = await fetchAs.json(url); // OR fetchAsJson(url);

  console.log('# json', jsonData.data);
  // {
  //   "status": 200,
  //   "message": "OK",
  //   "by": "fetch-as"
  // }
}

runFetch();

For TypeScript users, you are recommended to install the required typing file from @types/node-fetch as one of the devDependencies for the package to work properly as some of the typings used in the package are from the said typing file but they are not included as part of the bundle.

Otherwise, see Options for a list of supported options.

$ npm install --dev @types/node-fetch

// Interface
interface FetchAsInfo {
  size: number;
  timeout: number;
  type: "basic"|"cors"|"default"|"error"|"opaque"|"opaqueredirect";
  headers: {
    [key: string]: any;
  };
}

// Interface
interface FetchAsReturnType<T = any, U = any> {
  status: number;
  info: FetchAsInfo;

  data?: T;
  error?: U;
}

• status <string> HTTP response status code. Any response that has a HTTP status greater than 399 can be regarded as an error response.

• info <Object> This contains additional information you might need from a response. See FetchAsInfo for the detailed interface.

  • size <number> Response size.
  • timeout <number> Response timeout.
  • type <string> Response type. Possible values are: basic, cors, default, error, opaque, opaqueredirect.
  • headers <Object> Response headers, e.g. { 'content-type': 'application/json' }.

• data <?any> This contains the successful response data of the user-specified type, for instance, MyReturnData in the example shown above. Only shows when the HTTP response status code is less than 400.

• error <?any> This contains the error response data of type T. Only shows when the HTTP response status code is greater than 399.

Each return type have default Generics type of any which means it can be any type in JavaScript and is overridable by user defined type via TypeScript's Generics.

// e.g. Overridable Generics
interface SuccessData {
  message: string;
}

...
const d = await FetchAsJson<SuccessData>(...);

// d will have the type of `FetchAsReturnType<SuccessData, any>>`
assert(d.data.message, '...'); // OK
...

This contains a collection of methods that will convert the response into the specified data type:

• .arrayBuffer(url[, options]) Method which will return a ArrayBuffer.
• .blob(url[,options]) Method which will return a Blob.
• .buffer(url[, options]) Method which will return a Buffer.
• .json(url[, options]) Method which will return a JSON data which can consumed by JavaScript as Object.
• .text(url[, options]) Method which will return a text/ string.
• .textConverted(url[, options]) Method which will return a text/ string, except instead of always converting to UTF-8, encoding sniffing will be performed and text converted to UTF-8, if possible.

• url <string> A string representing the URL for fetching.
• options <?Object> Options for HTTP(S) request. See @types/node-fetch for TypeScript users to see the explanation.
• returns: <Promise<FetchAsReturnType<ArrayBuffer>> Promise which resolves with a FetchAsReturnType of type ArrayBuffer.

• url <string> A string representing the URL for fetching.
• options <?Object> Options for HTTP(S) request. See @types/node-fetch for TypeScript users to see the explanation.
• returns: <Promise<FetchAsReturnType<Blob>> Promise which resolves with a FetchAsReturnType of type Blob.

• url <string> A string representing the URL for fetching.
• options <?Object> Options for HTTP(S) request. See @types/node-fetch for TypeScript users to see the explanation.
• returns: <Promise<FetchAsReturnType<Buffer>> Promise which resolves with a FetchAsReturnType of type Buffer.

• url <string> A string representing the URL for fetching.
• options <?Object> Options for HTTP(S) request. See @types/node-fetch for TypeScript users to see the explanation.
• returns: <Promise<FetchAsReturnType<Object>> Promise which resolves with a FetchAsReturnType of type JSON which can consumed by JavaScript as Object.

• url <string> A string representing the URL for fetching.
• options <?Object> Options for HTTP(S) request. See @types/node-fetch for TypeScript users to see the explanation.
• returns: <Promise<FetchAsReturnType<string>> Promise which resolves with a FetchAsReturnType of type string.

* Please note that encoding is required to be installed in order to use this method.

• Identical to fetchAsText(url[, options]), except instead of always converting to UTF-8, encoding sniffing will be performed and text converted to UTF-8, if possible.

MIT License © Rong Sen Ng