http-link-header

What is http-link-header?

The http-link-header npm package is used to parse and construct HTTP Link headers. It provides a convenient way to handle the Link header, which is used in HTTP responses to provide metadata about the requested resource, such as pagination links, relationships, and more.

What are http-link-header's main functionalities?

Parsing Link Headers

This feature allows you to parse a Link header string into an object. The parsed object contains references (refs) that you can easily access and manipulate.

const LinkHeader = require('http-link-header');
const linkHeader = LinkHeader.parse('<https://api.example.com/users?page=2>; rel="next", <https://api.example.com/users?page=5>; rel="last"');
console.log(linkHeader.refs);

Constructing Link Headers

This feature allows you to construct a Link header string from an object. You can add multiple links with different relations and then convert the object back to a string format suitable for HTTP headers.

const LinkHeader = require('http-link-header');
const linkHeader = new LinkHeader();
linkHeader.set({
  uri: 'https://api.example.com/users?page=2',
  rel: 'next'
});
linkHeader.set({
  uri: 'https://api.example.com/users?page=5',
  rel: 'last'
});
console.log(linkHeader.toString());

Finding Links by Relation

This feature allows you to find a specific link by its relation type (rel). This is useful for quickly accessing specific links like 'next', 'prev', 'first', or 'last' in paginated responses.

const LinkHeader = require('http-link-header');
const linkHeader = LinkHeader.parse('<https://api.example.com/users?page=2>; rel="next", <https://api.example.com/users?page=5>; rel="last"');
const nextLink = linkHeader.get('rel', 'next');
console.log(nextLink);

Other packages similar to http-link-header

parse-link-header

The parse-link-header package is another library for parsing HTTP Link headers. It provides similar functionality to http-link-header but focuses solely on parsing and does not offer construction capabilities. It is simpler and may be preferred if you only need to parse Link headers.

http-headers

The http-headers package is a more general library for parsing and constructing HTTP headers, including but not limited to Link headers. It offers a broader range of functionality compared to http-link-header, making it suitable for more complex HTTP header manipulations.

README

HTTP Link Header

Parse & format HTTP link headers according to RFC 8288

Install via npm

$ npm install --save http-link-header

Deviations from the RFC

Link Target

While RFC 8288, Section 3.1 states that relative URI-References MUST be resolved by the parsers – this library DOES NOT. This is due to the parser not having an input for the absolute or canonical URI of the related document. Currently there are no plans to add this, and it is left to the user whether or not to resolve relative URIs.

Usage

var LinkHeader = require( 'http-link-header' )

Parsing a HTTP link header

var link = LinkHeader.parse(
  '<example.com>; rel="example"; title="Example Website", ' +
  '<example-01.com>; rel="alternate"; title="Alternate Example Domain"'
)

> Link {
  refs: [
    { uri: 'example.com', rel: 'example', title: 'Example Website' },
    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
  ]
}

Checking whether it has a reference with a given attribute & value

link.has( 'rel', 'alternate' )
> true

Retrieving a reference with a given attribute & value

link.get( 'rel', 'alternate' )
> [
  { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' }
]

// Shorthand for `rel` attributes
link.rel( 'alternate' )
> [
  { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' }
]

Setting references

link.set({ uri: 'https://example.com/next', rel: 'next' })
> Link {
  refs: [
    { uri: 'example.com', rel: 'example', title: 'Example Website' },
    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
    { rel: 'next', uri: 'https://example.com/next' }
  ]
}

Setting a unique reference

link.setUnique({
  uri: 'https://example.com/image.png',
  rel: 'preload',
  as: 'image',
  type: 'image/png'
})
> Link {
  refs: [
    { uri: 'https://example.com/image.png', rel: 'preload', as: 'image', type: 'image/png' }
  ]
}

link.setUnique({
  uri: 'https://example.com/image.png',
  rel: 'preload',
  as: 'image',
  type: 'image/png'
})
> Link {
  refs: [
    { uri: 'https://example.com/image.png', rel: 'preload', as: 'image', type: 'image/png' }
  ]
}

Parsing multiple headers

var link = new LinkHeader()

link.parse( '<example.com>; rel="example"; title="Example Website"' )
> Link {
  refs: [
    { uri: 'example.com', rel: 'example', title: 'Example Website' },
  ]
}

link.parse( '<example-01.com>; rel="alternate"; title="Alternate Example Domain"' )
> Link {
  refs: [
    { uri: 'example.com', rel: 'example', title: 'Example Website' },
    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
  ]
}

link.parse( '<example-02.com>; rel="alternate"; title="Second Alternate Example Domain"' )
> Link {
  refs: [
    { uri: 'example.com', rel: 'example', title: 'Example Website' },
    { uri: 'example-01.com', rel: 'alternate', title: 'Alternate Example Domain' },
    { uri: 'example-02.com', rel: 'alternate', title: 'Second Alternate Example Domain' },
  ]
}

Handling extended attributes

link.parse( '</extended-attr-example>; rel=start; title*=UTF-8\'en\'%E2%91%A0%E2%93%AB%E2%85%93%E3%8F%A8%E2%99%B3%F0%9D%84%9E%CE%BB' )

> Link {
  refs: [
    { uri: '/extended-attr-example', rel: 'start', 'title*': { language: 'en', encoding: null, value: '①⓫⅓㏨♳𝄞λ' } }
  ]
}

Stringifying to HTTP header format

link.toString()
> '<example.com>; rel=example; title="Example Website", <example-01.com>; rel=alternate; title="Alternate Example Domain"'

Speed

$ npm run benchmark

# http-link-header .parse() ⨉ 1000000
ok ~1.29 s (1 s + 289696759 ns)

# http-link-header #toString() ⨉ 1000000
ok ~554 ms (0 s + 553782657 ns)