Talk is cheap. Show me the code.

const { Client, errors } = require('elasticsearch')
const client = new Client({
  host: 'http://localhost:9200',
  plugins: [utility]
})

async function run () {
  try {
    const body = await client.search({
      index: 'game-of-thrones',
      body: {
        query: {
          match: { quote: 'winter' }
        }
      }
      ignore: [404]
    })
    console.log(body)
  } catch (err) {
    if (err instanceof errors.BadRequest) {
      console.log('Bad request')
    } else {
      console.log(err)
    }
  }
}

function utility (Client, config, components) {
  const ca = components.clientAction.factory
  Client.prototype.utility = components.clientAction.namespaceFactory()
  const utility = Client.prototype.utility.prototype

  utility.index = ca({
    params: {
      refresh: {
        type: 'enum',
        options: [
          'true',
          'false',
          'wait_for',
          ''
        ]
      },
    },
    urls: [
      {
        fmt: '/<%=index%>/_doc',
        req: {
          index: {
            type: 'string',
            required: true
          }
        }
      }
    ],
    needBody: true,
    method: 'POST'
  })
})

const { Client, errors } = require('@elastic/elasticsearch')
// NOTE: `host` has been renamed to `node`,
//       and `plugins` is no longer supported
const client = new Client({ node: 'http://localhost:9200' })

async function run () {
  try {
    // NOTE: we are using the destructuring assignment
    const { body } = await client.search({
      index: 'game-of-thrones',
      body: {
        query: {
          match: { quote: 'winter' }
        }
      }
    // NOTE: `ignore` now is in a separated object
    }, {
      ignore: [404]
    })
    console.log(body)
  } catch (err) {
    // NOTE: we are checking the `statusCode` property
    if (err.statusCode === 400) {
      console.log('Bad request')
    } else {
      console.log(err)
    }
  }
}

// NOTE: we can still extend the client, but with  a different API.
//       This new API is a little bit more verbose, since you must write
//       your own validations, but it's way more flexible.
client.extend('utility.index', ({ makeRequest, ConfigurationError }) => {
  return function utilityIndex (params, options) {
    const { body, index, ...querystring } = params
    if (body == null) throw new ConfigurationError('Missing body')
    if (index == null) throw new ConfigurationError('Missing index')
    const requestParams = {
      method: 'POST',
      path: `/${index}/_doc`,
      body: body,
      querystring
    }
    return makeRequest(requestParams, options)
  }
})