You can get started with AI21Labs’ Jurassic family of models, as well as see a full list of available foundational models, by signing up for an API key on their website. Here’s an example of initializing an instance in LangChain.js:
See this section for general instructions on installing integration packages.
npm
npm install @langchain/community @langchain/core

import { AI21 } from "@langchain/community/llms/ai21";

const model = new AI21({
  ai21ApiKey: "YOUR_AI21_API_KEY", // Or set as process.env.AI21_API_KEY
});

const res = await model.invoke(`Translate "I love programming" into German.`);

console.log({ res });

/*
  {
    res: "\nIch liebe das Programmieren."
  }
 */