# browser-headers

> > Compatibility Layer for the Headers class

Latest version **0.4.1** (published 2018-11-24) · Apache-2.0 license · 0 weekly downloads

## Install

```sh
npm install browser-headers
pnpm add browser-headers
yarn add browser-headers
bun add browser-headers
```

## Health

**Score 25/100 (F)** — status: abandoned.

Positive: has types; no vulnerabilities; high quality score.

Warnings: low downloads; no esm support; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.4.1 |
| Published | 2018-11-24 |
| First published | 2017-02-28 |
| Weekly downloads | 0 |
| License | Apache-2.0 |
| TypeScript types | bundled |
| Module format | CommonJS |
| Dependencies | 0 |
| Unpacked size | 54.3 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 13 |
| Maintainers | jonnyreeves, marcuslongmuir |
| Keywords | headers, fetch |

## Links

- npm: https://www.npmjs.com/package/browser-headers
- Repository: https://github.com/improbable-eng/js-browser-headers
- Homepage: https://github.com/improbable-eng/js-browser-headers#readme
- Issues: https://github.com/improbable-eng/js-browser-headers/issues
- npm.io page: https://npm.io/package/browser-headers

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## Recent versions

- 0.4.1 (latest) — 2018-11-24
- 0.4.0 — 2017-12-03
- 0.3.2 — 2017-03-31
- 0.3.1 — 2017-03-14
- 0.3.0 — 2017-03-14
- 0.2.1 — 2017-03-09
- 0.2.0 — 2017-03-09
- 0.1.7 — 2017-03-03
- 0.1.6 — 2017-03-02
- 0.1.5 — 2017-03-02
- 0.1.4 — 2017-03-02
- 0.1.3 — 2017-03-01
- 0.1.2 — 2017-03-01
- 0.1.1 — 2017-03-01
- 0.1.0 — 2017-02-28

## README

# browser-headers
> Compatibility Layer for the Headers class

[![Master Build](https://travis-ci.org/improbable-eng/js-browser-headers.svg?branch=master)](https://travis-ci.org/improbable-eng/js-browser-headers)
![BrowserStack Status](https://www.browserstack.com/automate/badge.svg?badge_key=MVZzVGFiVXpFRjFjRmZ2SUpJaWlGam9Xa2c0R1B6MnVBV25aZm43cDZtUT0tLXZaMDdRR0pVbVFyRVBmd0p1TUNlZVE9PQ==--8b1eb510ef6bde3d6d89b2d65b033a9030f75f6f%)
[![NPM](https://img.shields.io/npm/v/browser-headers.svg)](https://www.npmjs.com/package/browser-headers)
[![Apache 2.0 License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](LICENSE)
![quality: beta](https://img.shields.io/badge/quality-beta-yellow.svg)

The [Headers](https://fetch.spec.whatwg.org/#headers-class) class defined in the [fetch spec](https://fetch.spec.whatwg.org/) has been implemented slightly differently across browser vendors at the time of writing (Feb 2017).

This package intends to provide a wrapper for the `Headers` class to ensure a consistent API and provides headers parsing from CLRF-delimited strings.

This package is written in TypeScript, but is designed to be used just as easily by JavaScript projects.


## Installation
via npm:

```bash
$ npm install browser-headers
```

## Browser Support
This library is tested against Chrome, Safari, Firefox, Opera, Edge, IE 10 and IE 9.

## API

```js
import BrowserHeaders from 'browser-headers';

const headers = new BrowserHeaders({
  "content-type": "application/json",
  "my-header": ["value-one","value-two"]
});

headers.forEach((key, values) => {
  console.log(key, values);
});

// Output:
// "content-type", ["application/json"]
// "my-header", ["value-one","value-two"]
```

The `BrowserHeaders` class has the following methods:

#### constructor(init: Headers | {[key: string]: string|string[]} | Map<string,string|string[]> | string | BrowserHeaders, options: {splitValues: boolean}): string[]
`init` can be one of:
* An instance of `Headers`
* A CLRF-delimited string (e.g. `key-a: one\r\nkey-b: two`)
* An instance of `BrowserHeaders`
* An object consisting of `string->(string|string[])` (e.g. `{"key-a":["one","two"],"key-b":"three"}`) 
* A `Map<string, string|string[]>`

The constructor takes an additional optional `options` parameter of `{ splitValues: boolean = false }`, where 
`splitValues` defines whether the header values should be split by comma (`,`) into separate strings - this is useful 
to unify the `.append` functionality of `Headers` implementations (see the warning at the end of this README). 
`splitValues` should be used with caution and defaults to `false` because it might split what is actually a single 
logical value that contained a `,`.

#### .get(key: string): string[]
Returns all of the values for that header `key` as an array

#### .forEach(callback: (key: string, values: string[]) => void): void
Invokes the provided callback with each key and it's associated values as an array

#### .set(key: string, values: string|string[]): void
Overwrites the `key` with the value(s) specified.

#### .append(key: string, values: string|string[]): void
Appends the value(s) to specified `key`.

#### .delete(key: string, value: string): void
If the `value` is specified: 
    Removes the specified `value` from the `key` if it is present.

Otherwise:
    Removes all values for the `key` if it is present.

#### .has(key: string, value?: string): boolean
If the value is specified: 
    Returns true if the `key` contains the corresponding `value`.

Otherwise:
    Returns true if the `key` has at least one value.

#### .appendFromString(str: string): void
Appends the headers defined in the provided CLRF-delimited string (e.g. `key-a: one\r\nkey-b: two`)

#### .toHeaders(): Headers
Returns an instance of the browser's `Headers` class. This will throw an exception if the current browser does not have
the `Headers` class.

## Warning about `.append` in native `Headers`
The `.append` function of the `Headers` class differs significantly between browsers.

Some browsers concatenate the values with `", "` or just `","` and others actually maintain the individual values such that
they can return later return an array. There is a constructor option (see above: `splitValues`) that can be enabled to
attempt to parse these concatenated strings back into individual values.
```js
const headers = new Headers();
headers.append("key-A", "one");
headers.append("key-A", "two");
const keyA = headers.get("key-A"); // or .getAll depending on the browser 
console.log(typeof keyA);
console.log(keyA);

// Output in Edge 14:
// string
// one, two

// Output in Safari 10:
// string
// one,two

// Output in Chrome 56:
// object
// ["one", "two"]
```

---
_Source: https://npm.io/package/browser-headers · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._