retry promise extension

retry_promise.js

/**
 * This script uses ECMAScript 2015 syntax.
 * Check compatibility for your environment.
 * To run it in nodejs (5.8.0) you need to enable feature flags:
 * --harmony_destructuring --harmony_rest_parameters --harmony_default_parameters
 */
"use strict"


/**
 * This will create callback function which tries to execute handler given times and returns promise.
 * It will perserve and forward original arguments to the handler.
 *
 * @param {function} handler - function to be retried
 * @param {object} options - reTry options
 * @param {integer} options.times - number of times to try execute function
 * @param {integer} options.timeout - timeout applied between attempts
 * @param {function} options.log - optional logging function
 */
function reTry(handler, { times = 3, timeout = 100, log = (() => undefined) } = {}) {
    return (...args) => function tryIt() {
        return Promise.resolve().then(() => handler(...args)).catch(err => {
            if (times > 0) {
                log(`Retrying promise, remaining attempts: ${times - 1}`, err)
                return new Promise(resolve => setTimeout(resolve, timeout)).then(() => tryIt(handler, args, --times));
            }
            return Promise.reject(err);
        });
    }();
}


let failedCount = 2;

function sumArray(arr) {
    if (failedCount) {
        failedCount--;
        throw new Error('Expected error');
    }
    return arr.reduce((a, b) => a + b);
}

const opts = { times: 4, timeout: 1000, log: console.error };

Promise.resolve([1, 2, 3, 4])
       .then(reTry(sumArray, opts))
       .then(sum => console.log(`Sum of array: ${sum}`));