Create the browser script

This topic is part of a tutorial that create an Amazon Lex chatbot within a web application to engage your web site visitor. To start at the beginning of the tutorial, see Building an Amazon Lex chatbot.

Create a file named index.js. Copy and paste the code below into index.js. Import the required Amazon SDK for JavaScript modules and commands. Create clients for Amazon Lex, Amazon Comprehend, and Amazon Translate. Replace REGION with Amazon Region, and IDENTITY_POOL_ID with the ID of the identity pool you created in the Create the Amazon resources . To retrieve this identity pool ID, open the identity pool in the Amazon Cognito console, choose Edit identity pool, and choose Sample code in the side menu. The identity pool ID is shown in red text in the console.

First, create a libs directory create the required service client objects by creating three files, comprehendClient.js, lexClient.js, and translateClient.js. Paste the approriate code below into each, and replace REGION and IDENTITY_POOL_ID in each.

import { CognitoIdentityClient } from "@aws-sdk/client-cognito-identity";
import { fromCognitoIdentityPool } from "@aws-sdk/credential-provider-cognito-identity";
import { ComprehendClient } from "@aws-sdk/client-comprehend";

const REGION = "REGION";
const IDENTITY_POOL_ID = "IDENTITY_POOL_ID"; // An Amazon Cognito Identity Pool ID.

// Create an Amazon Comprehend service client object.
const comprehendClient = new ComprehendClient({
  region: REGION,
  credentials: fromCognitoIdentityPool({
    client: new CognitoIdentityClient({ region: REGION }),
    identityPoolId: IDENTITY_POOL_ID,
  }),
});

export { comprehendClient };

import { CognitoIdentityClient } from "@aws-sdk/client-cognito-identity";
import { fromCognitoIdentityPool } from "@aws-sdk/credential-provider-cognito-identity";
import { LexRuntimeServiceClient } from "@aws-sdk/client-lex-runtime-service";

const REGION = "REGION";
const IDENTITY_POOL_ID = "IDENTITY_POOL_ID"; // An Amazon Cognito Identity Pool ID.

// Create an Amazon Lex service client object.
const lexClient = new LexRuntimeServiceClient({
  region: REGION,
  credentials: fromCognitoIdentityPool({
    client: new CognitoIdentityClient({ region: REGION }),
    identityPoolId: IDENTITY_POOL_ID,
  }),
});

export { lexClient };

import { CognitoIdentityClient } from "@aws-sdk/client-cognito-identity";
import { fromCognitoIdentityPool } from "@aws-sdk/credential-provider-cognito-identity";
import { TranslateClient } from "@aws-sdk/client-translate";

const REGION = "REGION";
const IDENTITY_POOL_ID = "IDENTITY_POOL_ID"; // An Amazon Cognito Identity Pool ID.

// Create an Amazon Translate service client object.
const translateClient = new TranslateClient({
  region: REGION,
  credentials: fromCognitoIdentityPool({
    client: new CognitoIdentityClient({ region: REGION }),
    identityPoolId: IDENTITY_POOL_ID,
  }),
});

export { translateClient };

This code is available here on GitHub..

Next, create an index.js file, and paste the code below into it.

Replace BOT_ALIAS and BOT_NAME with the alias and name of your Amazon Lex bot respectively, and USER_ID with a user id. The createResponse asynchronous function does the following:

import { DetectDominantLanguageCommand } from "@aws-sdk/client-comprehend";
import { TranslateTextCommand } from "@aws-sdk/client-translate";
import { PostTextCommand } from "@aws-sdk/client-lex-runtime-service";
import { lexClient } from "./libs/lexClient.js";
import { translateClient } from "./libs/translateClient.js";
import { comprehendClient } from "./libs/comprehendClient.js";

var g_text = "";
// Set the focus to the input box.
document.getElementById("wisdom").focus();

function showRequest() {
  var conversationDiv = document.getElementById("conversation");
  var requestPara = document.createElement("P");
  requestPara.className = "userRequest";
  requestPara.appendChild(document.createTextNode(g_text));
  conversationDiv.appendChild(requestPara);
  conversationDiv.scrollTop = conversationDiv.scrollHeight;
}

function showResponse(lexResponse) {
  var conversationDiv = document.getElementById("conversation");
  var responsePara = document.createElement("P");
  responsePara.className = "lexResponse";

  var lexTextResponse = lexResponse;

  responsePara.appendChild(document.createTextNode(lexTextResponse));
  responsePara.appendChild(document.createElement("br"));
  conversationDiv.appendChild(responsePara);
  conversationDiv.scrollTop = conversationDiv.scrollHeight;
}

function handletext(text) {
  g_text = text;
  var xhr = new XMLHttpRequest();
  xhr.addEventListener("load", loadNewItems, false);
  xhr.open("POST", "../text", true); // A Spring MVC controller
  xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded"); //necessary
  xhr.send("text=" + text);
}

function loadNewItems() {
  showRequest();

  // Re-enable input.
  var wisdomText = document.getElementById("wisdom");
  wisdomText.value = "";
  wisdomText.locked = false;
}

// Respond to user's input.
const createResponse = async () => {
  // Confirm there is text to submit.
  var wisdomText = document.getElementById("wisdom");
  if (wisdomText && wisdomText.value && wisdomText.value.trim().length > 0) {
    // Disable input to show it is being sent.
    var wisdom = wisdomText.value.trim();
    wisdomText.value = "...";
    wisdomText.locked = true;
    handletext(wisdom);

    const comprehendParams = {
      Text: wisdom,
    };
    try {
      const data = await comprehendClient.send(
        new DetectDominantLanguageCommand(comprehendParams)
      );
      console.log(
        "Success. The language code is: ",
        data.Languages[0].LanguageCode
      );
      const translateParams = {
        SourceLanguageCode: data.Languages[0].LanguageCode,
        TargetLanguageCode: "en", // For example, "en" for English.
        Text: wisdom,
      };
      try {
        const data = await translateClient.send(
          new TranslateTextCommand(translateParams)
        );
        console.log("Success. Translated text: ", data.TranslatedText);
        const lexParams = {
          botName: "BookTrip",
          botAlias: "mynewalias",
          inputText: data.TranslatedText,
          userId: "chatbot", // For example, 'chatbot-demo'.
        };
        try {
          const data = await lexClient.send(new PostTextCommand(lexParams));
          console.log("Success. Response is: ", data.message);
          var msg = data.message;
          showResponse(msg);
        } catch (err) {
          console.log("Error responding to message. ", err);
        }
      } catch (err) {
        console.log("Error translating text. ", err);
      }
    } catch (err) {
      console.log("Error identifying language. ", err);
    }
  }
};
// Make the function available to the browser.
window.createResponse = createResponse;

This code is available here on GitHub..

Now use webpack to bundle the index.js and Amazon SDK for JavaScript modules into a single file, main.js.