Url-reference NPM

URLReference

"URL or Relative Reference"

The URLReference class is designed to overcome shortcomings of the URL class.

Features

Supports Relative and scheme-less URLs.
Supports Nullable Components.
Distinct Rebase, Normalize and Resolve methods.
Resolve is Behaviourally Equivalent with the WHATWG URL Standard.

Examples

new URLReference ('filename.txt#top', '//host') .href
// => '//host/filename.txt#top'

new URLReference ('?do=something', './path/to/resource') .href
// => './path/to/resource?do=something'

new URLReference ('take/action.html') .resolve ('http://🌲') .href
// => 'http://xn--vh8h/take/action.html'

API

Summary

The module exports a single class URLReference with nullable properties (getters/setters):

scheme,
username, password, hostname, port,
pathname, pathroot, driveletter, filename,
query, fragment.

It has three key methods:

rebase, normalize and resolve.

It can be converted to an ASCII, or to a Unicode string via:

the href getter and the toString method.

Terminology

Special: The WHATWG URL standard uses the phrase "special URL" for URLs that have a "special scheme". A "special scheme" is a scheme that is equivalent to http, https, ws, wss, ftp or file.
Hierarchical: The path of an URL may either be hierarchical or opaque. An hierarchical path is subdivided into smaller components, an opaque path is not.
(!) The path of a "special" URL is always hierarchical. The path of a non-special URL is hierarchical if the URL has an authority or otherwise if its path starts with a path-root /.
Rebase is a generalisation of reference transformation as defined in the RFC3986 (URI) that supports constructing relative references. The base argument may be a relative reference, in addition to an absolute URL.
Non-strict: The RFC3986 (URI) standard defines a strict and a non-strict variant of reference transformation. The non-strict variant ignores the scheme of the input if it is equivalent to the scheme of the base. The WHATWG uses the non-strict behaviour for "special" URLs and the strict behaviour for other URLs.

URLReference

Constructor

new URLReference ()
new URLReference (input)
new URLReference (input, base)

Constructs a new URLReference object. The result may represent a relative URL. The resolve method can be used to ensure that the result represents an absolute URL.

Arguments input and base are optional. Each may be a string to be parsed, or an existing URLReference object. If a base argument is supplied, then input is rebased onto base after parsing.

const r1 = new URLReference ();
// r.href == '' // The 'empty relative URL'

const r2 = new URLReference ('/big/trees/');
// r.href == '/big/trees/'

const r3 = new URLReference ('index.html', '/big/trees/');
// r.href == '/big/trees/index.html'

const r4 = new URLReference ('README.md', r3);
// r.href == '/big/trees/README.md'

Parsing behaviour

The parsing behaviour is adapted according to the scheme of input or the scheme of base otherwise.

The hostname is parsed as an opaque hostname string.
The parsing and validation of a hostname as a domain is done in the resolve method instead.
The invalid \ code-points before the host and in the path are converted to / if the input has a special scheme or if it has no scheme at all.
Windows drive letters are detected if the scheme is equivalent to file or if no scheme is present.
If no scheme is present and a windows drive letter is detected then then the scheme is implicitly set to file.

const r1 = new URLReference ('\\foo\\bar', 'http:')
// r1.href == 'http:/foo/bar'

const r2 = new URLReference ('\\foo\\bar', 'ofp:/')
// r2.href == 'ofp:/\\foo\\bar'

const r3 = new URLReference ('/c:/path/to/file')
// r3.href == 'file:/c:/path/to/file'
// r3.hostname == null
// r3.driveletter == 'c:'

const r4 = new URLReference ('/c:/path/to/file', 'http:')
// r4.href == 'http:/c:/path/to/file'
// r4.hostname == null
// r4.driveletter == null

Methods

Rebase – urlReference .rebase (base)

The base argument may be a string or an URLReference object.

Rebase implements a slight generalisation of reference transformation as defined in RFC3986 (URI). Rebase returns a new URLReference instance, or throws an error if the base argument reprensents an URL with an opaque path.

Rebase applies a "non-strict" reference transformation to URLReferences that have a "special scheme". This legacy behaviour is required to achieve compatibility with the WHATWG URL Standard.

Note: A "non-strict reference transformation" ignores the scheme of the input if it matches the scheme of the base. This has a surprising consequence: An URLReference that has a special scheme may still behave as a relative URL:

const base = new URLReference ('http://host/dir/')
const rel = new URLReference ('http:?do=something')
const rebased = rel.rebase (base)
// rebased.href == 'http://host/dir/?do=something'

Rebase applies a "strict" reference transformation to non-special URLReferences. The strict variant does not remove the scheme from the input.

const base = new URLReference ('ofp://host/dir/')
const abs = new URLReference ('ofp:?do=something')
const rebased = abs.rebase (base)
// rebased.href == 'ofp:?do=something'

It is not possible to rebase a relative URLReference on a base that has an opaque path.

const base = new URLReference ('ofp:this/is/an/opaque-path/')
const rel = new URLReference ('filename.txt')
// const rebased = rel.rebase (base) // throws:
// TypeError: Cannot rebase <filename.txt> onto <ofp:this/is/an/opaque-path/>

const base2 = new URLReference ('ofp:/not/an/opaque-path/')
const rebased = rel.rebase (base2) // This works as expected
// rebased.href == 'ofp:/not/an/opaque-path/filename.txt'

Normalize – urlReference .normalize ()

Normalize collapses dotted segments in the path, removes default ports and percent encodes certain code-points. It behaves in the same way as the WHATWG URL constructor, except for the fact that it supports relative URLs. Normalize always returns a new URLReference instance.

Resolve

urlReference .resolve ()
urlReference .resolve (base)

The optional base argument may be a string or an existing URLReference object.

Resolve returns a new URLReference that represents an absolute URL, or throws an error if this is not possible. It uses the same forceful error correcting behaviour as the WHATWG URL constructor.

Note: An unpleasant aspect of the WHATWG behaviour is that if the input is a non-file special URL, and the input has no authority, then the first non-empty path component will be coerced to an authority:

const r1 = new URLReference ('http:/foo/bar')
// r.host == null
// r.pathname == '/foo/bar'

const r2 = r1.resolve ('http://host/')
// The scheme of r1 is ignored because it matches the base.
// Thus the hostname is taken from the base.
// r2.href == 'http://host/foo/bar'

const r3 = r1.resolve ()
// r1 does not have an authority, so the first non-empty path
// component `foo` is coerced into an authority for the result.
// r1.href == 'http://foo/bar'

Resolve does additional processing and checks on the authority:

Asserts that file-URLs and web-URLs have an authority.
Asserts that the authority of web-URLs is not empty.
Asserts that file-URLs do not have a username, password or port.
Parses opaque hostnames of file-URLs and web-URLs as a domain or an ip-address.

String – urlReference .toString ()

Converts the URLReference to a string. This preserves unicode characters in the URL, unlike the href getter which ensures that the result consists of ASCII code-points only.

new URLReference ('take/action.html') .resolve ('http://🌲') .toString ()
// => 'http://🌲/take/action.html'

new URLReference ('take/action.html') .resolve ('http://🌲') .href
// => 'http://xn--vh8h/take/action.html'

Properties

Access to the components of the URLReference goes through the following getters/setters. All properties are nullable, however some invariants are maintained.

scheme
username
password
hostname
port
pathname

driveletter
pathroot
filename

query
fragment

Licence

MIT Licenced.