LangChain.js Has a Free API That Chains LLM Calls Into Complex AI Workflows

LangChain.js lets you build multi-step AI workflows: chain prompts, connect to databases, search the web, use tools — all orchestrated in TypeScript. Quick Setup npm install langchain @langchain/openai Basic Chain import { ChatOpenAI } from " @langchain/openai " import { ChatPromptTemplate } from " @langchain/core/prompts " import { StringOutputParser } from " @langchain/core/output_parsers " const model = new ChatOpenAI ({ model : " gpt-4o " }) const prompt = ChatPromptTemplate . fromMessages ([ [ " system " , " You translate {input_language} to {output_language} " ], [ " human " , " {input} " ] ]) const chain = prompt . pipe ( model ). pipe ( new StringOutputParser ()) const result = await chain . invoke ({ input_language : " English " , output_language : " French " , input : " I love programming " }) RAG (Retrieval-Augmented Generation) import { ChatOpenAI , OpenAIEmbeddings } from " @langchain/openai " import { MemoryVectorStore } from " langchain/vectorstores/memory " import { Rec