我的目标是从 NG2-webapp 内正在运行的本地 ElasticSearch 服务器 检索示例数据，然后显示这些结果。

到目前为止，我已经使用 NPM Elasticsearch Typescript 包 创建了一个组件 test-es-types 。

这是 .ts 代码：

  import { Component, OnInit } from '@angular/core';
  import * as elasticsearch from 'elasticsearch';

  @Component({
    selector: 'app-test-es-types',
    templateUrl: './test-es-types.component.html',
    styleUrls: ['./test-es-types.component.scss']
  })

  export class TestEsTypesComponent implements OnInit {

    constructor() { }

    ngOnInit() {

   // Setting up Elasticsearch Client
   var client = new elasticsearch.Client({
     host: 'http://localhost:9200',
     log: 'trace'
   });

   console.log("Client:", client);

  // Elasticsearch Server Ping
  client.ping({
  // ping usually has a 3000ms timeout
  requestTimeout: 1000
}, function (error) {
  if (error) {
    console.trace('elasticsearch cluster is down!');
  } else {
    console.log('All is well');
  }
});

// first we do a search, and specify a scroll timeout
var allTitles: string[] = [];
console.log("Erzeuge allTitles Array...");
client.search({
  index: 'bank',
  // Set to 30 seconds because we are calling right back
  scroll: '30s',
  searchType: 'query_then_fetch',
  docvalueFields: [''],
  q: 'Avenue'
}, function getMoreUntilDone(error, response) {
  // collect the first name from each response
  console.log("allTitles gefüllt: ", allTitles);
  response.hits.hits.forEach(function (hit) {
    allTitles.push(hit.fields.firstname);
  });

  if (response.hits.total !== allTitles.length) {
    // now we can call scroll over and over
    client.scroll({
      scrollId: response._scroll_id,
      scroll: '30s'
    }, getMoreUntilDone);
  } else {
    console.log('every "test" title', allTitles);
  }
});

}

}

ES-server 正在 localhost:9200 上运行并按预期返回查询的数据（根据控制台）。但是，当我尝试将这些数据放入数组 (allTitles) 时，我收到以下控制台错误：

Uncaught TypeError: Cannot read property 'firstname' of undefined

console.log 告诉我 allTitles 为空 (长度为 0)，因此这显然不起作用。看来我还不了解将对象转换为数组的复杂性？