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funtch - Functional Fetch

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Fetch based on isomorphic-fetch with functional and customizable behavior.

Getting started

Add dependency to your project

npm i -S funtch


Full documentation is available here.

Full usage example in example folder


import funtch from 'funtch';

funtch.get('https://api.github.com').then(data => doSomething(data))


const funtch = require('funtch');

funtch.get('https://api.github.com').then(data => doSomething(data))


You can send HTTP requests from common verbs by invoking the following methods from funtch:

Methode name Params Description
get url: String Perform a GET
post url: String
body: Any
Perform a POST with given body and Content-type guessed from param
put url: String
body: Any
Perform a PUT with given body and Content-type guessed from param
patch url: String
body: Any
Perform a PATCH with given body and Content-type guessed from param
delete url: String Perform a DELETE

If default pattern doesn't match your needs, you can build a step by step request by invoking funtch.url(url: String) and applying following methods:

Methode name Params Description
header key: String
value: String
Add HTTP header
auth value: String Add Authorization Header with given value
contentJson Add Content-type: application/json header
contentText Add Content-type: test/plain header
guessContentType body: Any Guess content type by checking if body is a JSON. If true, content is set to JSON, otherwise to text
acceptJson Add Accept: application/json header
acceptText Add Accept: text/plain header
content See content handler
error See error handler
body body: Any
guess: Boolean default true
Set body content of request, and guessing content on the fly
get Set method to GET and send request
post body: Any Set method to POST, add body if provided with content guess and send request
put body: Any Set method to PUT, add body if provided with content guess and send request
patch body: Any Set method to PATCH, add body if provided with content guess and send request
delete Set method to DELETE and send request
method method: String Set HTTP method to given value
send Send request as it

All these method are chainable and once send, the result is a Promise.

const fetchPromise = funtch
  .auth('Basic SECRET')
  .post({ star: true});

  .then(data => console.log(data))
  .catch(err => console.error(data));

Error Handling

By default, funtch will reject promise with an object describing error if HTTP status is greater or equal than 400. This object contains HTTP status, response headers and content (in plain text or JSON, according to content handler).

  status: 404,
  headers: {
    'content-length': '19',
    'content-type': 'text/plain; charset=utf-8',
    date: 'Sat, 06 May 2017 11:58:38 GMT',
    'x-content-type-options': 'nosniff',
    connection: 'close'
  content: '404 page not found',


Custom content handler

By default, fetch expose only two methods for reading content : text() and json(). Instead of juggling with these methods, funtch return content by examining Content-Type header and call one of the two methods.

You can easily override default content handler by calling content() on the build. The content handler method accept a reponse and return a Promise. Method is also passed to error handler method, in order to read content while identifying error.

Below an example that parse XML response.

import funtch, { CONTENT_TYPE_HEADER, CONTENT_TYPE_HEADER } from 'funtch';

const contentTypeJsonRegex = new RegExp(funtch.MEDIA_TYPE_JSON, 'i');
const contentTypeXmlRegex = /application\/xml/i;

function xmlContent(response) {
  if (contentTypeJsonRegex.test(response.headers.get(funtch.CONTENT_TYPE_HEADER))) {
    return response.json();

  return new Promise(resolve => {
    response.text().then(data => {
      if (contentTypeXmlRegex.test(response.headers.get(funtch.CONTENT_TYPE_HEADER))) {
        resolve(new DOMParser().parseFromString(data, 'text/xml'));


Custom error handler

By default, fetch return a valid Promise without considering http status. Funtch error handler is called first, in this way, you can identify an error response and reject the Promise. By default, if HTTP status is greather or equal than 400, it's considered as error.

You can easyly override default error handler by calling error() on the builder. The error handler method accept a response and return a Promise. You can reimplement it completely or adding behavior of the default one.

Below an example that add a toString() behavior.

import funtch, { errorHandler } from 'funtch';

function errorWithToString(response) {
  return new Promise((resolve, reject) =>
    errorHandler(response).then(resolve).catch(err =>
        toString: () => {
          if (typeof err.content === 'string') {
            return err.content;
          return JSON.stringify(err.content);

  .catch(err => console.log(String(err)));