Hierarchical configuration of JSON XHR communication for your APIs

JSON, AJAX, XHR, config, API, javascript, promise, restful
bower install jcx


Posterior Put a nice front on your backend! Posterior gives your remote APIs intuitive, Promise-based, JSON-ready JavaScript interfaces via flexible, declarative, hierarchical configurations.

Download: posterior.min.js or posterior.js
NPM: npm install posterior

Build Status npm version npm


var GitHub = new Posterior({
    url: 'https://api.github.com',
    load: function() {
        console.log('Requested:', this.cfg.url);
    ESHA: {
        url: '/repos/esha/{0}',
        Version: {
            follows: 'tags_url',
            then: function(tags) {
                return tags[0].name;
}, 'GitHub');


What Is This?

Posterior is a tool to handle encapsulation and configuration of "AJAX" calls. It takes a structured configuration and converts it into a hierarchy of functions that, when called, composes the desired request and response behaviors and returns a Promise. That Promise will resolve (or reject) when all the configured request and response handling has completed.

Apart from the basic XHR encapsulation and handling, Posterior provides a number of high level features commonly needed for interacting with remote resources. These include interpolating URLs, waiting for required dependencies to be resolved, throttling request rates, caching, following URLS in linked resources, singleton resources, automatic retry for failed requests, and more. The intent of this encapsulation is to allow client-side developers to keep implementation details of their interactions with remote servers out of their client-side logic. All translation between the data the client requests/receives and the data the server expects/returns can be hidden behind a friendly, Promise-returning function.

Release History

  • 2014-09-08 v0.1.4 (initial)
  • 2014-09-09 v0.2.3 (debug mode, preprocess, no global)
  • 2014-09-16 v0.3.1 (timeout->error, async fix, direct XHR cfg, status mapping)
  • 2014-09-17 v0.4.0 (retry options, css activity notification)
  • 2014-09-19 v0.5.4 (XHR tests, json cfg shortcut, better structure, safer copy, responseObject property, et al)
  • 2014-09-24 v0.6.2 (s/serialize/transformData, s/preprocess/configure, better debug output)
  • 2014-10-13 v0.7.3 (support all XHR events, JSON default, resolve/reject promise with response/error, request/responseData handler support)
  • 2015-03-12 v0.9.3 (switch to better Promise polyfill, rename to Posterior, support 'parent' property, expose config props with getters)
  • 2015-07-28 v0.10.1 (fix retry, cache, and require features)
  • 2015-08-05 v0.11.0 (support both ${key} and {key} in URL templates)
  • 2015-08-08 v0.12.0 (s/share(d)Result/save(d)Result, and support dynamic link relations via new 'follows' property)
  • 2015-08-13 v0.13.0 (upgrade config string filling to also resolve args by index and nested data)
  • 2016-05-18 v0.14.1 (support failure listener for non-200 status codes, pass XHR to configured catch functions, don't override specified Accept or Content-Type headers)
  • 2016-05-20 v0.15.0 (API.resolve can now support repeated replacements when consuming data, consume array data, and is easier to use as util)
  • 2016-05-23 v0.16.0 (add throttle:{key,ms} support)
  • 2017-03-27 v0.17.0 (distinguish subfunction from props via capitalization or @, bind then/catch functions to built cfg)
  • 2017-09-12 v0.18.1 (s/saveResult/singleton, handle JSON parse errors suppressed by browser, make presence of document optional)
  • 2017-10-26 v0.19.3 (initial TypeScript support, module export support)
  • 2017-11-22 v0.20.0 (support property metadata as structured object--not just key prefixes--to be more TypeScript friendly)
  • 2017-12-04 v0.21.4 (add 'Children' and 'Properties' subconfigs, since TypeScript can't handle mix of known and unknown keys with typed values)
  • 2018-01-18 v0.21.5 (change index.d.ts to match format that seems to be working for store2 and moment.js)
  • 2018-01-19 v0.21.6 (misc bug fixes)
  • 2018-02-12 v0.22.7 ('capture' debug mode, notable index.d.ts fixes/changes, stop binding all functions to metaCfg context)
  • 2019-11-26 v0.22.9 (mostly build infrastructure upgrades)