delayed-promises

Resolve an array of promises, one after another but with delays

All notable changes to this project are documented in CHANGELOG.md file.

Idea

The main purpose of this library is to delay resolving of succeeding promises:

                 delay                       delay
|----------|----------------|----------|---------------|-->

^                           ^
Resolve a first promise       Resolve a second promise

Installation

Run npm install delayed-promises --save to install the library.

Usage

Importing

Import the module

const delayedPromises = require('delayed-promises');

Invoking

Invoke delayedPromises method with the following arguments

delayedPromises(data, options).then(results => ... );

data

An object with data to be used to build each request

options

An object with configuration properties, implementing following interface:

interface IDefaultOptions {
  delay: number;
  delayFirst: boolean;
  createPromiseFn: () => Promise<any>;
  extractResponseFn: (response: any) => any;
  middlewareFn: (response: any) => void;
  extractErrorFn: (error: any) => any;
}

Example of default options:

const defaultOptions = {
  delay: 1000,
  delayFirst: false,
  createPromiseFn: null,
  extractResponseFn: response => response,
  middlewareFn: response => response,
  extractErrorFn: error => error.message,
}

• delay - delay between promises
• delayFirst - define whether first request should be delayed or not
• createPromiseFn - callback function to create a promise to be resolved later
• extractResponseFn - callback function to extract incoming data from http client
• middlewareFn - callback function for different purposes, like logging data
• extractErrorFn - callback function to extract incoming data from error object

Example

Examples to run locally

Examples with axios or fetch clients can be found in "examples" directory. To run these examples, clone repo and run following commands:

npm install
npm run example:axios
npm run example:fetch

Full example

const axios = require('axios');
const delayedPromises = require('delayed-promises');

delayedPromises(
  [
    'https://httpbin.org/delay/0',
    'https://httpbin.org/delay/0',
    'https://httpbin.org/delay/0',
  ],
  {
    createPromiseFn: dataRow => axios.get(dataRow),
    extractResponseFn: response => response.data,
  }
)
.then((results) => {
  console.log(results);
})