# web.header

## Function

Sets a response header or set of response headers.

## Syntax

```bt
web.header(key, value)
web.header(headers)
```

## Parameters

| Parameters | Type | Required | Default value | Description |
| ------ | ------ | ------ | ------ | ------ |
| key | String | No | None | Response header name. |
| value | Any | No | None | Response header value. |
| headers | Object | No | None | Response header mapping object; rules for keys and values are given below. |

## headers object structure

| key | value type | description |
| ------ | ------ | ------ |
| Response header name | Any | Response header value; when called, it will be converted into a string and written into the HTTP response header. |

## Return value

| Type | Description |
| ------ | ------ |
| Bool | Returns true if the setting is successful. |

## Example

```bt
// Usage 1: set one response header.
web.header('Content-Type', 'text/plain; charset=utf-8')

// Usage 2: set multiple response headers at once.
result = web.header({
    'Content-Type': 'text/plain; charset=utf-8',
    'Access-Control-Allow-Origin': '*'
})

// Output: true
print result
```

## Notes

- Can only be called in a web request.
- Parameters must be objects or key/value.