headers-utils

headers-utils

Utilities for working with a Headers instance.

Motivation

Various request issuing libraries utilize a different format of headers. This library chooses the Headers instance as the middle-ground between server and client, and provides functions to convert that instance to primitives and vice-versa.

Getting started

$ npm install headers-utils

Headers ⭢ N

headersToString: (h: Headers): string

headersToString(
  new Headers({
    connection: 'keep-alive',
    'content-type': ['text/plain', 'image/png'],
  })
)
// connetion: keep-alive
// content-type: text/plain, image/png

headersToList: (h: Headers): Array<[string, string | string[]]>

headersToList(
  new Headers({
    connection: 'keep-alive',
    'content-type': ['text/plain', 'image/png'],
  })
)
// [['connection', 'keep-alive'], ['content-type', ['text/plain', 'image/png']]]

headersToObject: (h: Headers): Record<string, string | string[]>

headersToObject(
  new Headers({
    connection: 'keep-alive',
    'content-type': ['text/plain', 'image/png'],
  })
)
// { connection: 'keep-alive', 'content-type': ['text/plain', 'image/png'] }

N ⭢ Headers

stringToHeaders: (s: string): Headers

const stringToHeaders(`
connection: keep-alive
content-type: text/plain, image/png
`)
// Headers { connection: 'keep-alive', 'content-type': ['text/plain', 'image/png'] }

listToHeaders: (l: Array<[string, string | string[]]>): Headers

listToHeaders([
  ['connection', 'keep-alive'],
  ['content-type', ['text/plain', 'image/png']],
])
// Headers { connection: 'keep-alive', 'content-type': ['text/plain', 'image/png'] }

objectToHeaders: (o: Record<string, string | string[]>): Headers

objectToHeaders({
  connection: 'keep-alive',
  'content-type': ['text/plain', 'image/png'],
})
// Headers { connection: 'keep-alive', 'content-type': ['text/plain', 'image/png'] }

---

Utilities

reduceHeadersObject: <R>(o: Record<string, string | string[]>, reducer: (acc: R, name: string, value: string | string[]) => R) => R

reduceHeadersObject <
  HeadersObject >
  ({
    Accept: '*/*',
    'Content-Type': ['application/json', 'text/plain'],
  },
  (headers, name, value) => {
    headers[name.toLowerCase()] = value
    return headers
  },
  {})
// { 'accept': '*/*', 'content-type': ['application/json', 'text/plain'] }

appendHeader: (o: Record<string, string | string[]>, n: string, v: string | string[]): Record<string, string | string[]>

appendHeader(
  { 'content-type': 'application/json' },
  'content-type',
  'text/plain'
)
// { 'content-type': ['application/json', 'text/plain']}

flattenHeadersList: (l: Array<[string, string | string[]]>): Array<string, string>

flattenHeadersList([['content-type', ['text/plain', 'image/png']]])
// ['content-type', 'text/plain; image/png']

flattenHeadersObject: (o: Record<string, string | string[]>): Record<string, string>

flattenHeadersObject({
  'content-type': ['text/plain', 'image/png'],
})
// { 'content-type': 'text/plain; image/png' }