api/middleware/sendJSON.js

var check = require('check-types');

function sendJSONResponse(req, res, next) {

  // do nothing if no result data set
  if (!res || !check.object(res.body) || !check.object(res.body.geocoding)) {
    return next();
  }

  // default status
  var statusCode = 200;

  // vary status code whenever an error was reported
  var geocoding = res.body.geocoding;
  if( check.array( geocoding.errors ) && geocoding.errors.length ){

    // default status for errors is 400 Bad Request
    statusCode = 400; // 400 Bad Request

    // iterate over all reported errors
    geocoding.errors.forEach( function( err ){
      // custom status codes for instances of the Error() object.
      if( err instanceof Error ){
        // we can extract the error type from the constructor name
        switch( err.constructor.name ){
          // elasticsearch errors
          // see: https://github.com/elastic/elasticsearch-js/blob/master/src/lib/errors.js
          case 'RequestTimeout': statusCode = 408; break; // 408 Request Timeout
          case 'NoConnections': statusCode = 502; break; // 502 Bad Gateway
          case 'ConnectionFault': statusCode = 502; break; // 502 Bad Gateway
          case 'Serialization': statusCode = 500; break; // 500 Internal Server Error
          case 'Generic': statusCode = 500; break; // 500 Internal Server Error
          default: statusCode = 500; // 500 Internal Server Error
        }
      }
    });
  }

  // respond
  return res.status(statusCode).json(res.body);
}

module.exports = sendJSONResponse;