Util

A small set of utility helpers exposed for third-party implementations of the Dispatcher API. They cover the header-handling primitives undici uses internally, so that custom dispatchers and handlers can normalize header names and parse raw header lists exactly the way undici does.

import { util } from 'undici'

const { parseHeaders, headerNameToString } = util

parseHeaders(headers, obj?): Record

Receives a flat list of raw header name/value pairs and returns them as an object keyed by lowercased header name. Header names are normalized with headerNameToString(), and Buffer values are decoded as latin1. When a header name appears more than once, its values are collected into an array.

import { util } from 'undici'

const raw = ['Content-Type', 'text/plain', 'Set-Cookie', 'a=1', 'Set-Cookie', 'b=2']

console.log(util.parseHeaders(raw))
// { 'content-type': 'text/plain', 'set-cookie': [ 'a=1', 'b=2' ] }

headerNameToString(value): string

Returns the lowercased form of a header name. The value may be provided as a <string> or as a <Buffer>, in which case it is decoded as latin1. Common header names are resolved through an internal lookup table for performance.

import { util } from 'undici'

console.log(util.headerNameToString('Content-Type'))
// 'content-type'

console.log(util.headerNameToString(Buffer.from('X-Custom-Header')))
// 'x-custom-header'