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*   Prompts
*   Custom template formats

On this page

Alternate prompt template formats
=================================

The primary template format for LangChain prompts is the simple and versatile `f-string`. LangChain.js supports [`handlebars`](https://handlebarsjs.com/) as an experimental alternative.

Note that templates created this way cannot be added to the LangChain prompt hub and may have unexpected behavior if you're using tracing.

Setup[​](#setup "Direct link to Setup")
---------------------------------------

You'll need to install the [handlebars](https://www.npmjs.com/package/handlebars) templating engine package:

    npm install handlebars

Usage[​](#usage "Direct link to Usage")
---------------------------------------

    import { HandlebarsPromptTemplate } from "langchain/experimental/prompts/handlebars";import { ChatAnthropic } from "@langchain/anthropic";import { StringOutputParser } from "@langchain/core/output_parsers";const template = `Tell me a joke about {{topic}}`;const prompt = HandlebarsPromptTemplate.fromTemplate(template);const formattedResult = await prompt.invoke({ topic: "bears" });console.log(formattedResult);/*  StringPromptValue {    value: 'Tell me a joke about bears'  }*/const model = new ChatAnthropic();const chain = prompt.pipe(model).pipe(new StringOutputParser());const result = await chain.invoke({  topic: "bears",});console.log(result);/*  Why did the bears dissolve their hockey team? Because there were too many grizzly fights!*/

#### API Reference:

*   [HandlebarsPromptTemplate](https://api.js.langchain.com/classes/langchain_experimental_prompts_handlebars.HandlebarsPromptTemplate.html) from `langchain/experimental/prompts/handlebars`
*   [ChatAnthropic](https://api.js.langchain.com/classes/langchain_anthropic.ChatAnthropic.html) from `@langchain/anthropic`
*   [StringOutputParser](https://api.js.langchain.com/classes/langchain_core_output_parsers.StringOutputParser.html) from `@langchain/core/output_parsers`

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