Amazon Lex provides both build and runtime endpoints. Each endpoint provides a set of operations (API). Your conversational bot uses the runtime API to understand user utterances (user input text or voice). For example, suppose a user says "I want pizza", your bot sends this input to Amazon Lex using the runtime API. Amazon Lex recognizes that the user request is for the OrderPizza intent (one of the intents defined in the bot). Then Amazon Lex engages in user conversation on behalf of the bot to elicit required information (slot values, such as pizza size and crust type), and then performs fulfillment activity (that you configured when you created the bot). You use the build-time API to create and manage your Amazon Lex bot. For a list of build-time operations, see the build-time API, .

Installing

To install this package, simply type add or install @aws-sdk/client-lex-runtime-service using your favorite package manager:

npm install @aws-sdk/client-lex-runtime-service
yarn add @aws-sdk/client-lex-runtime-service
pnpm add @aws-sdk/client-lex-runtime-service

Getting Started

Import

The AWS SDK is modulized by clients and commands. To send a request, you only need to import the LexRuntimeServiceClient and the commands you need, for example GetSessionCommand:

// ES5 example
const { LexRuntimeServiceClient, GetSessionCommand } = require("@aws-sdk/client-lex-runtime-service");

// ES6+ example
import { LexRuntimeServiceClient, GetSessionCommand } from "@aws-sdk/client-lex-runtime-service";

Usage

To send a request, you:

Initiate client with configuration (e.g. credentials, region).
Initiate command with input parameters.
Call send operation on client with command object as input.
If you are using a custom http handler, you may call destroy() to close open connections.

// a client can be shared by different commands.
const client = new LexRuntimeServiceClient({ region: "REGION" });

const params = {
  /** input parameters */
};
const command = new GetSessionCommand(params);

Async/await

We recommend using await operator to wait for the promise returned by send operation as follows:

// async/await.
try {
  const data = await client.send(command);
  // process data.
} catch (error) {
  // error handling.
} finally {
  // finally.
}

Async-await is clean, concise, intuitive, easy to debug and has better error handling as compared to using Promise chains or callbacks.

Promises

You can also use Promise chaining to execute send operation.

client.send(command).then(
  (data) => {
    // process data.
  },
  (error) => {
    // error handling.
  }
);

Promises can also be called using .catch() and .finally() as follows:

client
  .send(command)
  .then((data) => {
    // process data.
  })
  .catch((error) => {
    // error handling.
  })
  .finally(() => {
    // finally.
  });

Callbacks

We do not recommend using callbacks because of callback hell, but they are supported by the send operation.

// callbacks.
client.send(command, (err, data) => {
  // process err and data.
});

v2 compatible style

The client can also send requests using v2 compatible style. However, it results in a bigger bundle size and may be dropped in next major version. More details in the blog post on modular packages in AWS SDK for JavaScript

import * as AWS from "@aws-sdk/client-lex-runtime-service";
const client = new AWS.LexRuntimeService({ region: "REGION" });

// async/await.
try {
  const data = await client.getSession(params);
  // process data.
} catch (error) {
  // error handling.
}

// Promises.
client
  .getSession(params)
  .then((data) => {
    // process data.
  })
  .catch((error) => {
    // error handling.
  });

// callbacks.
client.getSession(params, (err, data) => {
  // process err and data.
});

Troubleshooting

When the service returns an exception, the error will include the exception information, as well as response metadata (e.g. request id).

try {
  const data = await client.send(command);
  // process data.
} catch (error) {
  const { requestId, cfId, extendedRequestId } = error.$metadata;
  console.log({ requestId, cfId, extendedRequestId });
  /**
   * The keys within exceptions are also parsed.
   * You can access them by specifying exception names:
   * if (error.name === 'SomeServiceException') {
   *     const value = error.specialKeyInException;
   * }
   */
}

Getting Help

Please use these community resources for getting help. We use the GitHub issues for tracking bugs and feature requests, but have limited bandwidth to address them.

Visit Developer Guide or API Reference.
Check out the blog posts tagged with aws-sdk-js on AWS Developer Blog.
Ask a question on StackOverflow and tag it with aws-sdk-js.
Join the AWS JavaScript community on gitter.
If it turns out that you may have found a bug, please open an issue.

To test your universal JavaScript code in Node.js, browser and react-native environments, visit our code samples repo.

Contributing

This client code is generated automatically. Any modifications will be overwritten the next time the @aws-sdk/client-lex-runtime-service package is updated. To contribute to client you can check our generate clients scripts.

License

This SDK is distributed under the Apache License, Version 2.0, see LICENSE for more information.

Client Commands (Operations List)

DeleteSession

Command API Reference / Input / Output

GetSession

Command API Reference / Input / Output

PostContent

Command API Reference / Input / Output

PostText

Command API Reference / Input / Output

PutSession

Command API Reference / Input / Output

FAQs

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Package last updated on 05 May 2025

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Install

@aws-sdk/client-lex-runtime-service