## Partial With Strings

One common use case for wanting to partial a prompt template is if you get some of the variables before others. For example, suppose you have a prompt template that requires two variables, `foo` and `baz`. If you get the `foo` value early on in the chain, but the `baz` value later, it can be annoying to wait until you have both variables in the same place to pass them to the prompt template. Instead, you can partial the prompt template with the `foo` value, and then pass the partialed prompt template along and just use that. Below is an example of doing this:

```typescript
import { PromptTemplate } from "langchain/prompts";

const prompt = new PromptTemplate({
  template: "{foo}{bar}",
  inputVariables: ["foo", "bar"]
});

const paritalPrompt = await prompt.partial({
  foo: "foo",
});

const formattedPrompt = await paritalPrompt.format({
  bar: "baz",
});

console.log(formattedPrompt);

// foobaz
```

You can also just initialize the prompt with the partialed variables.


```typescript
const prompt = new PromptTemplate({
  template: "{foo}{bar}",
  inputVariables: ["bar"],
  partialVariables: {
    foo: "foo",
  },
});

const formattedPrompt = await prompt.format({
  bar: "baz",
});

console.log(formattedPrompt);

// foobaz
```

## Partial With Functions

You can also partial with a function. The use case for this is when you have a variable you know that you always want to fetch in a common way. A prime example of this is with date or time. Imagine you have a prompt which you always want to have the current date. You can't hard code it in the prompt, and passing it along with the other input variables can be tedious. In this case, it's very handy to be able to partial the prompt with a function that always returns the current date.

```typescript
const getCurrentDate = () => {
  return new Date().toISOString();
};

const prompt = new PromptTemplate({
  template: "Tell me a {adjective} joke about the day {date}",
  inputVariables: ["adjective", "date"],
});

const partialPrompt = await prompt.partial({
  date: getCurrentDate,
});

const formattedPrompt = await partialPrompt.format({
  adjective: "funny",
});

console.log(formattedPrompt)

// Tell me a funny joke about the day 2023-07-13T00:54:59.287Z
```

You can also just initialize the prompt with the partialed variables:


```typescript
const prompt = new PromptTemplate({
  template: "Tell me a {adjective} joke about the day {date}",
  inputVariables: ["adjective"],
  partialVariables: {
    date: getCurrentDate,
  }
});

const formattedPrompt = await prompt.format({
  adjective: "funny",
});

console.log(formattedPrompt)

// Tell me a funny joke about the day 2023-07-13T00:54:59.287Z
```