const DiscoveryV1 = require('watson-developer-cloud/discovery/v1');
const fs = require('fs');

const discovery = new DiscoveryV1({
  username: 'YOUR USERNAME',
  password: 'YOUR PASSWORD',
  version_date: DiscoveryV1.VERSION_DATE_2017_08_01
});

discovery.updateJsonDocument(
  {
    environment_id: 'YOUR ENVIRONMENT ID',
    collection_id: 'YOUR COLLECTION ID',
    configuration_id: 'YOUR CONFIGURATION ID',
    file: {},
    metadata: { foo: 'bar' }
  },
  function(error, data) {
    if (error) {
      console.log(error);
    } else {
      console.log(data);
    }
  }
);