Wrapper around `window.fetch`

NetworkError.js

'use strict';

// http://stackoverflow.com/questions/31089801/extending-error-in-javascript-with-es6-syntax
class ExtendableError extends Error {
    constructor(message) {
        super();
        this.message = message;
        this.stack = (new Error()).stack;
        this.name = this.constructor.name;
    }
}

class NetworkError extends ExtendableError {
    constructor(message, status, json = {}) {
        super(message);
        this.status = status;
        this.response = json;
    }
}

export default NetworkError;

xhr.js

import NetworkError from '../utils/NetworkError';

function checkStatus(response) {
    if (response.ok) {
        return response;
    }
    throw response;
};

function parseJson(response) {
    if (response.status === 201 || response.status === 204) {
        return {};
    }
    return response.json();
};

function parseError(response) {
    // Handle HTTP error statuses
    if (response && typeof response.json === 'function') {
        return parseJson(response)
            .then(json => {
                throw new NetworkError(response.statusText, response.status, json);
            }, () => {
                throw new NetworkError(response.statusText, response.status);
            });
    }
    // Handle Network errors, e.g. cors etc.
    throw new NetworkError(response.message);
}

function xhr(url, params = {}) {
    params = Object.assign({
        headers: {
            'Accept': 'application/json',
            'Content-Type': 'application/json'
        }
    }, params);

    return fetch(url, params)
        .then(checkStatus)
        .then(parseJson, parseError);
};

export default xhr;

// Usage:
// xhr('/Users').then((data) => { console.log('success', data); }, (error) => { console.log('error', error); }).catch((error) => { console.log('runtime error', error); });