# Page Not Found

The URL `5/5.2.1` does not exist. This page may have been moved, renamed, or deleted.

## Suggested Pages

You may be looking for one of the following:
- [伍.2.1 什么是函数式编程？](https://coffe1891.gitbook.io/frontend-hard-mode-interview/id-5/2.-han-shu-shi-bian-cheng/5.2.1.md)
- [前言·写给有缘人](https://coffe1891.gitbook.io/frontend-hard-mode-interview/0.0.1.md)
- [叁.2.1 React Hooks究竟是什么？](https://coffe1891.gitbook.io/frontend-hard-mode-interview/id-3/2.react/3.2.1.md)
- [伍.2.2 JavaScript的函数式编程探索](https://coffe1891.gitbook.io/frontend-hard-mode-interview/id-5/2.-han-shu-shi-bian-cheng/5.2.2.md)
- [伍.2.3 Pointfree无参数风格编程](https://coffe1891.gitbook.io/frontend-hard-mode-interview/id-5/2.-han-shu-shi-bian-cheng/5.2.3.md)

## How to find the correct page

If the exact page cannot be found, you can still retrieve the information using the documentation query interface.

### Option 1 — Ask a question (recommended)

Perform an HTTP GET request on the documentation index with the `ask` parameter:

```
GET https://coffe1891.gitbook.io/frontend-hard-mode-interview/id-5/2.-han-shu-shi-bian-cheng/5.2.1.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

### Option 2 — Browse the documentation index

Full index: https://coffe1891.gitbook.io/frontend-hard-mode-interview/sitemap.md

Use this to discover valid page paths or navigate the documentation structure.

### Option 3 — Retrieve the full documentation corpus

Full export: https://coffe1891.gitbook.io/frontend-hard-mode-interview/llms-full.txt

Use this to access all content at once and perform your own parsing or retrieval. It will be more expensive.

## Tips for requesting documentation

Prefer `.md` URLs for structured content, append `.md` to URLs (e.g., `/frontend-hard-mode-interview/id-5/2.-han-shu-shi-bian-cheng/5.2.1.md`).

You may also use `Accept: text/markdown` header for content negotiation.