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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))

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).

  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)));