# acceptsOptions

**Kind:** Interface

**Source:** [`src/helper/accepts/accepts.ts`](https://github.com/honojs/hono/blob/main/src/helper/accepts/accepts.ts#L17)

**Part of:** [Helper](subsystem-src-helper)

`acceptsOptions` defines the contract for matching a list of `Accept` values against an `acceptsConfig`. Its `match` method receives the available accept entries and configuration, then returns the selected value as a string.

## Properties

| Property | Type |
|---|---|
| `match` | `(accepts: Accept[], config: acceptsConfig) => string` |

## Diagram

```mermaid
graph LR
  A[Accept[]] --> C[acceptsOptions.match]
  B[acceptsConfig] --> C
  C --> D[string]
```

## Usage

```ts
import type { acceptsOptions } from './src/helper/accepts/accepts';

const options: acceptsOptions = {
  match(accepts, config) {
    const match = accepts.find((accept) => accept.type === config.type);

    return match?.type ?? '';
  },
};

const selected = options.match(accepts, config);
```

## AI Coding Instructions

- Implement `match` with both the `Accept[]` input and `acceptsConfig` input in mind.
- Return a string for every match path, including when no `Accept` entry matches.
- Keep matching rules consistent with the `Accept` and `acceptsConfig` types used by the accepts helper.
- Avoid mutating the incoming `accepts` array or `config` object during matching.

## How it works

`acceptsOptions` is the options interface accepted by `accepts(c, options)`. It extends `acceptsConfig`, so callers must set:

- `header`: one of `'Accept'`, `'Accept-Charset'`, `'Accept-Encoding'`, `'Accept-Language'`, `'Accept-Patch'`, `'Accept-Post'`, or `'Accept-Ranges'`. [src/helper/accepts/accepts.ts:11-18](src/helper/accepts/accepts.ts#L11-L18) [src/utils/headers.ts:345-352](src/utils/headers.ts#L345-L352)
- `supports`: an array of strings against which parsed accept-value `type` fields are compared. [src/helper/accepts/accepts.ts:11-15](src/helper/accepts/accepts.ts#L11-L15) [src/helper/accepts/accepts.ts:21-24](src/helper/accepts/accepts.ts#L21-L24)
- `default`: the string returned when the configured request header is absent or when the selected matcher finds no supported type. [src/helper/accepts/accepts.ts:14](src/helper/accepts/accepts.ts#L14) [src/helper/accepts/accepts.ts:42-44](src/helper/accepts/accepts.ts#L42-L44) [src/helper/accepts/accepts.ts:21-24](src/helper/accepts/accepts.ts#L21-L24)

It optionally accepts `match`, a function with the signature `(accepts: Accept[], config: acceptsConfig) => string`. [src/helper/accepts/accepts.ts:17-19](src/helper/accepts/accepts.ts#L17-L19) `accepts` reads `options.header` from the request, parses its value, and calls this function with the parsed values and the same options object when `match` is set; otherwise it calls `defaultMatch`. [src/helper/accepts/accepts.ts:40-48](src/helper/accepts/accepts.ts#L40-L48)

Each element passed as the first `match` argument has `type`, `params`, and numeric `q` fields. [src/helper/accepts/accepts.ts:5-9](src/helper/accepts/accepts.ts#L5-L9) The parser initializes missing quality values to `1`, reads a `q` parameter when present, and returns an array of parsed values. [src/utils/accept.ts:163-167](src/utils/accept.ts#L163-L167) [src/utils/accept.ts:211-237](src/utils/accept.ts#L211-L237)

Without a custom `match`, `defaultMatch` sorts the parsed array by descending `q`, returns the first entry whose `type` occurs in `supports`, and otherwise returns `default`. [src/helper/accepts/accepts.ts:21-25](src/helper/accepts/accepts.ts#L21-L25) A custom matcher can choose different selection rules; the test demonstrates one that sorts ascending by `q` and returns the first supported type. [src/helper/accepts/accepts.test.ts:89-112](src/helper/accepts/accepts.test.ts#L89-L112)

There is no runtime validation of `header`, `supports`, `default`, or the return value of `match` in this code. If the request header is falsy, `accepts` returns `default` immediately and does not parse the header or call `match`. [src/helper/accepts/accepts.ts:41-48](src/helper/accepts/accepts.ts#L41-L48)