headers-utils

A Headers class polyfill and transformation library.

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.

Install

``bash
$ npm install headers-utils
`

Polyfill

This package exports the Headers class that polyfills the native window.Headers implementation. This allows you to construct and manage headers using the same API in non-browser environments.

`js
import { Headers } from 'headers-utils'

const headers = new Headers({
Accept: '/',
'Content-Type': 'application/json',
})

headers.get('accept') // "/"
`

Methods

The Headers polyfill instance supports the same methods as the standard Headers instance:

- .has()
- .get()
- .set()
- .append()
- .delete()
- .forEach()

As well as the iterator methods:

- .keys()
- .values()
- .entries()

$3

In addition, the polyfill instance has the following methods:

- .all()

Returns the object of the _normalized_ header name/value pairs.

`js
const headers = new Headers({
Accept: '/',
'Content-Type': 'application/json',
})

headers.all()
// { "accept": "/", "content-type": "application/json" }
`

- .raw()

Similar to the .all() method, .raw() returns an object consisting of the header name/value pairs, but preserving raw header names.

`js
const headers = new Headers({
Accept: '/',
'Content-Type': 'application/json',
})

headers.raw()
// { "Accept": "/", "Content-Type": "application/json" }
`

Transformations

$3

- headersToString: (h: Headers): string

`js
import { headersToString } from 'headers-utils'

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[]]>

`js
import { headersToList } from 'headers-utils'

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

`js
import { headersToObject } from 'headers-utils'

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

$3

- stringToHeaders: (s: string): Headers

`js
import { stringToHeaders } from 'headers-utils'


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

`js
import { listToHeaders } from 'headers-utils'

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

- objectToHeaders: (o: Record): Headers

`js
import { objectToHeaders } from 'headers-utils'

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

---

Utilities

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

`js
import { reduceHeadersObject } from 'headers-utils'

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, n: string, v: string | string[]): Record

`js
import { appendHeader } from 'headers-utils'

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

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

`js
import { flattenHeadersList } from 'headers-utils'

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

- flattenHeadersObject: (o: Record): Record

`js
import { flattenHeadersObject } from 'headers-utils'

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