Elasticsearch client builds for bower.
Install with bower
bower install elasticsearch
Add a <script> to your html file and off you go!:
<script src="/bower_components/elasticsearch/elasticsearch.js"></script>
<script>
  var client = elasticsearch.Client({
    host: 'localhost:9200'
  });
</script>
Use elasticsearch.angular.js instead. This will create an elasticsearch module with an esFactory that you can use.
/*
 * create your app module, specify "elasticsearch" as a dependency
 */
var app = angular.module('myApp', ['elasticsearch']);
/*
 * create a service, which provides your elasticsearch client
 * to other parts of your application
 */
app.service('es', function (esFactory) {
  return esFactory({
    host: 'localhost:9200',
    // ...
  });
});
Use elasticsearch.jquery.js instead. Rather than a global elasticsearch it will create a jQuery.es namespace.
var client = new $.es.Client({
  hosts: 'localhost:9200'
});