# entrypoint

> **Function** in `@langchain/langgraph`

📖 [View in docs](https://reference.langchain.com/javascript/langchain-langgraph/index/entrypoint)

Define a LangGraph workflow using the `entrypoint` function.

### Function signature

The wrapped function must accept at most **two parameters**. The first parameter
is the input to the function. The second (optional) parameter is a
LangGraphRunnableConfig object. If you wish to pass multiple parameters to
the function, you can pass them as an object.

### Helper functions

#### Streaming
To write data to the "custom" stream, use the getWriter function, or the
LangGraphRunnableConfig.writer property.

#### State management
The getPreviousState function can be used to access the previous state
that was returned from the last invocation of the entrypoint on the same thread id.

If you wish to save state other than the return value, you can use the
entrypoint.final function.

## Signature

```javascript
entrypoint<InputT, OutputT>(optionsOrName: string | EntrypointOptions, func: EntrypointFunc<InputT, OutputT>): Pregel<Record<string, PregelNode<InputT, EntrypointReturnT<OutputT>>>, __type, Record<string, unknown>, InputT, EntrypointReturnT<OutputT>, any, Awaited<EntrypointReturnT<OutputT>>>
```

## Parameters

| Name | Type | Required | Description |
|------|------|----------|-------------|
| `optionsOrName` | `string \| EntrypointOptions` | Yes | Either an EntrypointOptions object, or a string for the name of the entrypoint |
| `func` | `EntrypointFunc<InputT, OutputT>` | Yes | The function that executes this entrypoint |

## Returns

`Pregel<Record<string, PregelNode<InputT, EntrypointReturnT<OutputT>>>, __type, Record<string, unknown>, InputT, EntrypointReturnT<OutputT>, any, Awaited<EntrypointReturnT<OutputT>>>`

A Pregel instance that can be run to execute the workflow

## Methods

- [`final()`](https://reference.langchain.com/javascript/langchain-langgraph/index/entrypoint/final)

## Examples

### Example 1

```typescript
import { task, entrypoint } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";
import { interrupt, Command } from "@langchain/langgraph";

const composeEssay = task("compose", async (topic: string) => {
  await new Promise(r => setTimeout(r, 1000)); // Simulate slow operation
  return `An essay about ${topic}`;
});

const reviewWorkflow = entrypoint({
  name: "review",
  checkpointer: new MemorySaver()
}, async (topic: string) => {
  const essay = await composeEssay(topic);
  const humanReview = await interrupt({
    question: "Please provide a review",
    essay
  });
  return {
    essay,
    review: humanReview
  };
});

// Example configuration for the workflow
const config = {
  configurable: {
    thread_id: "some_thread"
  }
};

// Topic for the essay
const topic = "cats";

// Stream the workflow to generate the essay and await human review
for await (const result of reviewWorkflow.stream(topic, config)) {
  console.log(result);
}

// Example human review provided after the interrupt
const humanReview = "This essay is great.";

// Resume the workflow with the provided human review
for await (const result of reviewWorkflow.stream(new Command({ resume: humanReview }), config)) {
  console.log(result);
}
```

### Example 2

```typescript
import { entrypoint, getPreviousState } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";

const accumulator = entrypoint({
  name: "accumulator",
  checkpointer: new MemorySaver()
}, async (input: string) => {
  const previous = getPreviousState<number>();
  return previous !== undefined ? `${previous } ${input}` : input;
});

const config = {
  configurable: {
    thread_id: "some_thread"
  }
};
await accumulator.invoke("hello", config); // returns "hello"
await accumulator.invoke("world", config); // returns "hello world"
```

### Example 3

```typescript
import { entrypoint, getPreviousState } from "@langchain/langgraph";
import { MemorySaver } from "@langchain/langgraph-checkpoint";

const myWorkflow = entrypoint({
  name: "accumulator",
  checkpointer: new MemorySaver()
}, async (num: number) => {
  const previous = getPreviousState<number>();

  // This will return the previous value to the caller, saving
  // 2 * num to the checkpoint, which will be used in the next invocation
  // for the `previous` parameter.
  return entrypoint.final({
    value: previous ?? 0,
    save: 2 * num
  });
});

const config = {
  configurable: {
    thread_id: "some_thread"
  }
};

await myWorkflow.invoke(3, config); // 0 (previous was undefined)
await myWorkflow.invoke(1, config); // 6 (previous was 3 * 2 from the previous invocation)
```

---

[View source on GitHub](https://github.com/langchain-ai/langgraphjs/blob/dc37d3cd62bf88272cdc874e37354ae83ac01660/libs/langgraph-core/src/func/index.ts#L342)