JS tutorial doesnt seems to work

[SerLiang]

I am trying to do my project in Javascript. I followed the example here. Below is my code.

import { OpenAI } from "langchain/llms/openai";
import { RetrievalQAChain } from "langchain/chains";
import { HNSWLib } from "langchain/vectorstores/hnswlib";
import { OpenAIEmbeddings } from "langchain/embeddings/openai";
import { RecursiveCharacterTextSplitter } from "langchain/text_splitter";
import * as fs from "fs";
const filepath = 'src/documents/pvc-table-cloths.txt'

export const generateResponse = async (question: any) => {
  
  const OPENAI_API_KEY = process.env.OPENAI_API_KEY;
  
  const model = new OpenAI({});
  const text = fs.readFileSync(filepath, "utf8");
  const textSplitter = new RecursiveCharacterTextSplitter({ chunkSize: 1000 });
  const docs = await textSplitter.createDocuments([text]);

  // Create a vector store from the documents.
  const vectorStore = await HNSWLib.fromDocuments(docs, new OpenAIEmbeddings());

  // Create a chain that uses the OpenAI LLM and HNSWLib vector store.
  const chain = RetrievalQAChain.fromLLM(model, vectorStore.asRetriever());
  const res = await chain.call({
    query: question.toString(),
  });
  console.log({ res });
}

Whenever I ask question , the answer is either "I don't know" or returned me some portion of the documentation but not accurate answer. Can anyone tell me where am I missing?

Alternatively, When I do it in python, it works

from langchain.document_loaders import UnstructuredWordDocumentLoader
import nest_asyncio
nest_asyncio.apply()

loader = UnstructuredWordDocumentLoader("PVC Table Cloths.docx")

data = loader.load()

text_splitter = RecursiveCharacterTextSplitter(chunk_size=1000, chunk_overlap=0)
texts = text_splitter.split_documents(data)

embeddings = OpenAIEmbeddings()

db = FAISS.from_documents(texts, embeddings)

query = "this pvc curtain is black, I want clear. Please refund"

qa = RetrievalQA.from_chain_type(llm=OpenAI(), chain_type="stuff", retriever=db.as_retriever())
print(qa.run(query))

I try to convert the same python code to JS, however I am stuck in the part where Im unsure which is the JS version of RetrievalQA.from_chain_type.

Would appreciate anyone to point me to the right direction to figure out why it doesnt work on JS and how to make it work 🙏