LCEL pipe (|)

LangChain Expression Language (LCEL) uses the pipe operator to chain components: prompts, models, and output parsers.

Syntax

langchain

const chain = prompt | model | outputParser;

Example

langchain

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

const chain = ChatPromptTemplate.fromTemplate("Tell me a joke about {topic}")
  | model
  | new StringOutputParser();

const joke = await chain.invoke({ topic: "developers" });
console.log(joke);