LangChain.js Has a Free API — Here's How to Build AI Chains in JavaScript

LangChain.js is a framework for building LLM-powered applications. It provides abstractions for chains, agents, retrieval, and memory — making it easy to build complex AI workflows. Installation npm install langchain @langchain/openai @langchain/community Simple Chain import { ChatOpenAI } from " @langchain/openai " ; import { ChatPromptTemplate } from " @langchain/core/prompts " ; import { StringOutputParser } from " @langchain/core/output_parsers " ; const model = new ChatOpenAI ({ modelName : " gpt-4o-mini " }); const prompt = ChatPromptTemplate . fromMessages ([ [ " system " , " You are a technical writer. Write concise explanations. " ], [ " user " , " Explain {topic} in {style} style " ] ]); const chain = prompt . pipe ( model ). pipe ( new StringOutputParser ()); const result = await chain . invoke ({ topic : " web scraping " , style : " beginner-friendly " }); console . log ( result ); RAG (Retrieval-Augmented Generation) import { RecursiveCharacterTextSplitter } from " langcha