import { PromptTemplate } from "langchain/prompts";
import { ChatOpenAI } from "langchain/chat_models/openai";

const model = new ChatOpenAI({});
const promptTemplate = PromptTemplate.fromTemplate(
  "Tell me a joke about {topic}"
);

const chain = promptTemplate.pipe(model);

const result = await chain.invoke({ topic: "bears" });

console.log(result);

/*
  AIMessage {
    content: "Why don't bears wear shoes?\n\nBecause they have bear feet!",
  }
*/