AngularJS HTTP interceptor to work around CORS/JSONP problems

jsonp-proxy-request-interceptor.js

/**
 * @license CC0 1.0 (http://creativecommons.org/publicdomain/zero/1.0/)
 *
 * The problem:
 *   You need to make a cross-domain request for JSON data, but the remote
 *   server doesn't send the necessary CORS headers, and it only supports
 *   simple JSON-over-HTTP GET requests (no JSONP support).
 *
 * One possible solution:
 *   Use 'jsonp-proxy-request-interceptor' to proxy the request through
 *   https://jsonp.afeld.me/.
 *
 * Much thanks to Aidan Feldman for an awesome service!
 * <https://github.com/afeld/jsonp>
 * <https://jsonp.afeld.me/>
 */

var app = angular.module('jsonp-proxy-request-interceptor', []);

// (1) define a request interceptor
app.service('jsonpProxyRequestInterceptor',
    function JsonpProxyRequestInterceptor($log) {

  // (2) define a RegEx to extract raw JSON from the proxy response
  var callbackRx = /callback\((.+)\);/gm;

  this.request = function(config) {
    // (3) check if this is a request that needs to be proxied
    if (config.url === 'https://api.domain.com/' && config.method === 'GET') {

      // (4) save the API URL, and set request URL to 'https://jsonp.afeld.me/'
      var apiUrl = config.url;
      config.url = 'https://jsonp.afeld.me/';

      // (5) set the url= and callback= params for https://jsonp.afeld.me/
      config.params = angular.extend({}, config.params || {}, {
        url: apiUrl,
        callback: 'callback'
      });

      // (6) extract the raw JSON from the proxy response
      config.transformResponse.unshift(function(data, headers) {
        var matched = callbackRx.exec(data);
        // (7) pass the raw JSON along to the next transformer
        return matched ? matched[1] : data;
      });
    }

    // (8) return the (possibly modified) config
    return config;
  };

});

// (9) install the interceptor
app.config(['$httpProvider', function configHttp($httpProvider) {
  $httpProvider.interceptors.push('jsonpProxyRequestInterceptor');
}]);

// (10) stop banging your head against the wall