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https://github.com/mswjs/headers-polyfill
A Fetch API "Headers" polyfill and transformation library.
https://github.com/mswjs/headers-polyfill
fetch header headers http https polyfill request xmlhttprequest
Last synced: about 14 hours ago
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A Fetch API "Headers" polyfill and transformation library.
- Host: GitHub
- URL: https://github.com/mswjs/headers-polyfill
- Owner: mswjs
- License: mit
- Created: 2020-05-08T07:19:23.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2024-08-31T19:39:45.000Z (5 months ago)
- Last Synced: 2025-01-27T10:03:44.596Z (8 days ago)
- Topics: fetch, header, headers, http, https, polyfill, request, xmlhttprequest
- Language: TypeScript
- Homepage: https://npm.im/headers-polyfill
- Size: 489 KB
- Stars: 34
- Watchers: 5
- Forks: 11
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
[](https://www.npmjs.com/package/headers-polyfill)
# `headers-polyfill`
A `Headers` class polyfill and transformation library.
## Motivation
Various request issuing libraries utilize a different format of headers. This library chooses the [`Headers`](https://developer.mozilla.org/en-US/docs/Web/API/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-polyfill
```
## Polyfill
This package exports the `Headers` class that polyfills the native [`window.Headers`](https://developer.mozilla.org/en-US/docs/Web/API/Headers) implementation. This allows you to construct and manage headers using the same API in non-browser environments.
```js
import { Headers } from 'headers-polyfill'
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()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/has)
- [`.get()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/get)
- [`.set()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/set)
- [`.append()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/append)
- [`.delete()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/delete)
- [`.forEach()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/forEach)
- [`.getSetCookie()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/getSetCookie)
As well as the iterator methods:
- [`.keys()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/keys)
- [`.values()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/values)
- [`.entries()`](https://developer.mozilla.org/en-US/docs/Web/API/Headers/entries)
## Transformations
### `getRawHeaders()`
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" }
```
### Headers ⭢ N
- `headersToString: (h: Headers): string`
```js
import { headersToString } from 'headers-polyfill'
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-polyfill'
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-polyfill'
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`
```js
import { stringToHeaders } from 'headers-polyfill'
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-polyfill'
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-polyfill'
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-polyfill'
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-polyfill'
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-polyfill'
flattenHeadersList([['content-type', ['text/plain', 'image/png']]])
// ['content-type', 'text/plain, image/png']
```
- `flattenHeadersObject: (o: Record): Record`
```js
import { flattenHeadersObject } from 'headers-polyfill'
flattenHeadersObject({
'content-type': ['text/plain', 'image/png'],
})
// { 'content-type': 'text/plain, image/png' }
```