Simple fetch retry polyfill.

fetchRetry.polyfill.js

/**
 * Simple polyfill to support retry of fetch requests
 */
;(() => {
    global.fetchOriginal = global.fetch

    /**
     * Create retry fetch with last request arguments
     *
     * @param  {string}  resource request URL or resource to fetch
     * @param  {object}  options  options for request
     * @return {Function}         new fetch method
     */
    global.fetchRetry = (resource, options = {}) =>
        /**
         * Fetch method with preloaded request arguments
         * @param  {[type]} newOptions Override options of last request
         * @return {Promise}
         */
        (newOptions = {}) => {
            const mergedOptions = {
                ...options,
                ...newOptions,
                // reset signal option from previous fetch
                signal: newOptions.signal || undefined
            }

            return global.fetchOriginal(resource, mergedOptions)
        }

    /**
     * Override fetch and save last request arguments
     *
     * @param  {string}  resource request URL or resource to fetch
     * @param  {object}  options  options for request
     * @return {Promise}
     */
    global.fetch = async (resource, options) => {
        const response = await global.fetchOriginal(resource, options)
        response.fetchRetry = global.fetchRetry(resource, options)

        return response
    }
})()