# Jinja

A minimalistic JavaScript implementation of the Jinja templating engine, specifically designed for parsing and rendering ML chat templates.

## Usage

### Load template from a model on the Hugging Face Hub

First, install the jinja and hub packages:

```sh
npm i @huggingface/jinja
npm i @huggingface/hub
```

You can then load a tokenizer from the Hugging Face Hub and render a list of chat messages, as follows:

```js
import { Template } from "@huggingface/jinja";
import { downloadFile } from "@huggingface/hub";

const config = await (
	await downloadFile({
		repo: "mistralai/Mistral-7B-Instruct-v0.1",
		path: "tokenizer_config.json",
	})
).json();

const chat = [
	{ role: "user", content: "Hello, how are you?" },
	{ role: "assistant", content: "I'm doing great. How can I help you today?" },
	{ role: "user", content: "I'd like to show off how chat templating works!" },
];

const template = new Template(config.chat_template);
const result = template.render({
	messages: chat,
	bos_token: config.bos_token,
	eos_token: config.eos_token,
});
// "<s>[INST] Hello, how are you? [/INST]I'm doing great. How can I help you today?</s> [INST] I'd like to show off how chat templating works! [/INST]"
```

### Transformers.js

First, install the `@huggingface/jinja` and `@xenova/transformers` packages:

```sh
npm i @huggingface/jinja
npm i @xenova/transformers
```

You can then render a list of chat messages using a tokenizer's `apply_chat_template` method.

```js
import { AutoTokenizer } from "@xenova/transformers";

// Load tokenizer from the Hugging Face Hub
const tokenizer = await AutoTokenizer.from_pretrained("mistralai/Mistral-7B-Instruct-v0.1");

// Define chat messages
const chat = [
	{ role: "user", content: "Hello, how are you?" },
	{ role: "assistant", content: "I'm doing great. How can I help you today?" },
	{ role: "user", content: "I'd like to show off how chat templating works!" },
];

const text = tokenizer.apply_chat_template(chat, { tokenize: false });
// "<s>[INST] Hello, how are you? [/INST]I'm doing great. How can I help you today?</s> [INST] I'd like to show off how chat templating works! [/INST]"
```

Notice how the entire chat is condensed into a single string. If you would instead like to return the tokenized version (i.e., a list of token IDs), you can use the following:

```js
const input_ids = tokenizer.apply_chat_template(chat, { tokenize: true, return_tensor: false });
// [1, 733, 16289, 28793, 22557, 28725, 910, 460, 368, 28804, 733, 28748, 16289, 28793, 28737, 28742, 28719, 2548, 1598, 28723, 1602, 541, 315, 1316, 368, 3154, 28804, 2, 28705, 733, 16289, 28793, 315, 28742, 28715, 737, 298, 1347, 805, 910, 10706, 5752, 1077, 3791, 28808, 733, 28748, 16289, 28793]
```

For more information about chat templates, check out the transformers [documentation](https://huggingface.co/docs/transformers/main/en/chat_templating).