LangChain Hello World

Overview

Minimal working examples demonstrating LCEL (LangChain Expression Language) -- the .pipe() chain syntax that is the foundation of all LangChain applications.

Prerequisites

• Completed langchain-install-auth setup
• Valid LLM provider API key configured

Example 1: Simplest Chain (TypeScript)

import { ChatOpenAI } from "@langchain/openai";
import { ChatPromptTemplate } from "@langchain/core/prompts";
import { StringOutputParser } from "@langchain/core/output_parsers";

// Three components: prompt -> model -> parser
const prompt = ChatPromptTemplate.fromTemplate("Tell me a joke about {topic}");