FIWARE - Query Context Data from Web Browser

queryContext.js

// Don't forget to start Orion with the -corsOrigin option
// See also
var ORION_URL = 'http://130.206.83.68:1026/v1';
var QUERY_CONTEXT = ORION_URL + '/' + 'contextEntities'

function queryContext(entityId) {
  return new Promise(function(resolve, reject) {
    var xhr = new XMLHttpRequest();
    xhr.open('GET', QUERY_CONTEXT + '/' + entityId, true);

    xhr.responseType = 'json';
    xhr.setRequestHeader('Accept', 'application/json');

    xhr.onload = function() {
      if(xhr.status !== 200) {
        reject(xhr.status);
        return;
      }

    var response = xhr.response;
    var code = response.statusCode.code;
      switch(code) {
        case '200':
          resolve(response.contextElement);
        break;
        case '404':
          resolve(null);
        break;
        default:
          reject(code);
      }
    }

    xhr.onerror = reject;

    xhr.send();
  });
}

function doQuery(entityId) {
  queryContext(entityId).then(function(data) {
    if(data) {
      console.log('Data has been found: ', JSON.stringify(data));
    }
    else {
      console.log('Entity not found!');
    }
  }).catch(function(err) {
    console.error('Error while querying: ', err);
  });
}