Autolinker.js

Because I had so much trouble finding a good auto-linking implementation out in
the wild, I decided to roll my own. It seemed that everything I found out there
was either an implementation that didn't cover every case, or was just limited
in one way or another.

So, this utility attempts to handle everything. It:

• Autolinks URLs, whether or not they start with the protocol (i.e. 'http://').
  In other words, it will automatically link the text "google.com", as well as
  "http://google.com".
• Will properly handle URLs with special characters
• Will properly handle URLs with query parameters or a named anchor (i.e. hash)
• Will autolink email addresses.
• Will autolink phone numbers.
• Will autolink mentions (Twitter, Instagram, Soundcloud, TikTok).
• Will autolink hashtags.
• Will properly handle HTML input. The utility will not change the href
  attribute inside anchor (<a>) tags (or any other tag/attribute),
  and will not accidentally wrap the inner text of an anchor tag with a
  new one (which would cause doubly-nested anchor tags).

Hope that this utility helps you as well!

Full API Docs: http://gregjacobs.github.io/Autolinker.js/api/

Live Example: http://gregjacobs.github.io/Autolinker.js/examples/live-example/

v4.0 released September 2022

See Upgrading from v3.x -> v4.x (Breaking Changes) at the bottom of this readme.

Installation

Installing with the npm package manager:

 npm install autolinker --save

Installing with the Yarn package manager:

 yarn add autolinker

Installing with the Bower package manager:

 bower install Autolinker.js --save

Direct download

Simply clone this repository or download a zip of the project, and link to
either dist/Autolinker.js or dist/Autolinker.min.js with a script tag.

Importing Autolinker

ES6/TypeScript/Webpack:

 import Autolinker from 'autolinker';

Node.js:

 const Autolinker = require('autolinker');
// note: npm wants an all-lowercase package name, but the utility is a class and
// should be aliased with a capital letter

Browser

 <!-- 'Autolinker.js' or 'Autolinker.min.js' - non-minified is better for 
     debugging, minified is better for users' download time -->
<script src="path/to/autolinker/dist/Autolinker.min.js"></script>

Usage

Using the static link()
method:

 const linkedText = Autolinker.link(textToAutolink[, options]);

Using as a class:

 const autolinker = new Autolinker([ options ]);

const linkedText = autolinker.link(textToAutoLink);

Note: if using the same options to autolink multiple pieces of html/text, it is
slightly more efficient to create a single Autolinker instance, and run the
link()
method repeatedly (i.e. use the "class" form above).

Examples:

 const linkedText = Autolinker.link("Check out google.com");
// Produces: "Check out <a href="http://google.com" target="_blank" rel="noopener noreferrer">google.com</a>"

const linkedText = Autolinker.link("Check out google.com", { 
    newWindow: false 
});
// Produces: "Check out <a href="http://google.com">google.com</a>"

Options

The following are the options which may be specified for linking. These are
specified by providing an Object as the second parameter to Autolinker.link().
These include:

• newWindow : boolean
  
  true to have the links should open in a new window when clicked, false
  otherwise. Defaults to true.

• urls : boolean/Object
  
  true to have URLs auto-linked, false to skip auto-linking of URLs. Defaults
  to true.

  This option also accepts an Object form with 3 properties to allow for
  more customization of what exactly gets linked. All default to true:

  • schemeMatches (boolean): true to match URLs found prefixed with a scheme,
    i.e. http://google.com, or other+scheme://google.com, false to
    prevent these types of matches.
  • tldMatches: true to match URLs with known top level domains (.com, .net,
    etc.) that are not prefixed with a scheme (i.e. 'http://'). Ex: google.com,
    asdf.org/?page=1, etc. Set to false to prevent these types of matches.
  • ipV4Matches (boolean): true to match IPv4 addresses. Ex: 192.168.0.1.
    false to prevent these types of matches. Note that if the IP address had
    a prefixed scheme (such as 'http://'), and schemeMatches is true, it
    will still be linked.

  Example usage: urls: { schemeMatches: true, tldMatches: false, ipV4Matches: true }

• email : boolean
  
  true to have email addresses auto-linked, false to skip auto-linking of
  email addresses. Defaults to true.

• phone : boolean
  
  true to have phone numbers auto-linked, false to skip auto-linking of
  phone numbers. Defaults to true.

• mention : string
  
  A string for the service name to have mentions (@username) auto-linked to. Supported
  values at this time are 'twitter', 'soundcloud', 'instagram' and 'tiktok'. Pass false to skip
  auto-linking of mentions. Defaults to false.

• hashtag : boolean/string
  
  A string for the service name to have hashtags auto-linked to. Supported
  values at this time are 'twitter', 'facebook', 'instagram' and 'tiktok'. Pass false to skip
  auto-linking of hashtags. Defaults to false.

• stripPrefix : boolean
  
  true to have the 'http://' (or 'https://') and/or the 'www.'
  stripped from the beginning of displayed links, false otherwise.
  Defaults to true.

  This option also accepts an Object form with 2 properties to allow for
  more customization of what exactly is prevented from being displayed.
  Both default to true:

  • scheme (boolean): true to prevent the scheme part of a URL match
    from being displayed to the user. Example: 'http://google.com'
    will be displayed as 'google.com'. false to not strip the
    scheme. NOTE: Only an 'http://' or 'https://' scheme will be
    removed, so as not to remove a potentially dangerous scheme (such
    as 'file://' or 'javascript:').
  • www (boolean): true to prevent the 'www.' part of a URL match
    from being displayed to the user. Ex: 'www.google.com' will be
    displayed as 'google.com'. false to not strip the 'www'.

• stripTrailingSlash : boolean
  
  true to remove the trailing slash from URL matches, false to keep
  the trailing slash. Example when true: http://google.com/ will be
  displayed as http://google.com. Defaults to true.

• truncate : number/Object
  
  A number for how many characters long URLs/emails/Twitter handles/Twitter
  hashtags should be truncated to inside the text of a link. If the match is
  over the number of characters, it will be truncated to this length by
  replacing the end of the string with a two period ellipsis ('..').

  Example: a url like 'http://www.yahoo.com/some/long/path/to/a/file' truncated
  to 25 characters may look like this: 'yahoo.com/some/long/pat..'

  In the object form, both length and location may be specified to perform
  truncation. Available options for location are: 'end' (default), 'middle',
  or 'smart'. Example usage:

   truncate: { length: 32, location: 'middle' }
  

  The 'smart' truncation option is for URLs where the algorithm attempts to
  strip out unnecessary parts of the URL (such as the 'www.', then URL scheme,
  hash, etc.) before trying to find a good point to insert the ellipsis if it is
  still too long. For details, see source code of:
  TruncateSmart

• className : string
  
  A CSS class name to add to the generated anchor tags. This class will be added
  to all links, as well as this class plus "url"/"email"/"phone"/"hashtag"/"mention"
  suffixes for styling url/email/phone/hashtag/mention links differently.

  The name of the hashtag/mention service is also added as a CSS class for those
  types of matches.

  For example, if this config is provided as "my-link", then:

  • URL links will have the CSS classes: "my-link my-link-url"
  • Email links will have the CSS classes: "my-link my-link-email"
  • Phone links will have the CSS classes: "my-link my-link-phone"
  • Twitter mention links will have the CSS classes: "my-link my-link-mention my-link-twitter"
  • Instagram mention links will have the CSS classes: "my-link my-link-mention my-link-instagram"
  • Hashtag links will have the CSS classes: "my-link my-link-hashtag my-link-twitter"

• decodePercentEncoding: boolean
  
  true to decode percent-encoded characters in URL matches, false to keep
  the percent-encoded characters.

  Example when true: https://en.wikipedia.org/wiki/San_Jos%C3%A9 will
  be displayed as https://en.wikipedia.org/wiki/San_José.

  Defaults to true.

• replaceFn : Function
  
  A function to use to programmatically make replacements of matches in the
  input string, one at a time. See the section
  Custom Replacement Function for
  more details.

• sanitizeHtml : boolean
  

  true to HTML-encode the start and end brackets of existing HTML tags found
  in the input string. This will escape < and > characters to < and
  >, respectively.

  Setting this to true will prevent XSS (Cross-site Scripting) attacks,
  but will remove the significance of existing HTML tags in the input string. If
  you would like to maintain the significance of existing HTML tags while also
  making the output HTML string safe, leave this option as false and use a
  tool like https://github.com/cure53/DOMPurify (or others) on the input string
  before running Autolinker.

  Defaults to false.

For example, if you wanted to disable links from opening in new windows, you could do:

 const linkedText = Autolinker.link("Check out google.com", { 
    newWindow: false 
});
// Produces: "Check out <a href="http://google.com">google.com</a>"

And if you wanted to truncate the length of URLs (while also not opening in a new window), you could do:

 const linkedText = Autolinker.link("http://www.yahoo.com/some/long/path/to/a/file", { 
    truncate: 25, 
    newWindow: false 
});
// Produces: "<a href="http://www.yahoo.com/some/long/path/to/a/file">yahoo.com/some/long/pat..</a>"

More Examples

One could update an entire DOM element that has unlinked text to auto-link them
as such:

 const myTextEl = document.getElementById('text');
myTextEl.innerHTML = Autolinker.link(myTextEl.innerHTML);

Using the same pre-configured Autolinker
instance in multiple locations of a codebase (usually by dependency injection):

 const autolinker = new Autolinker({ newWindow: false, truncate: 25 });

//...

autolinker.link("Check out http://www.yahoo.com/some/long/path/to/a/file");
// Produces: "Check out <a href="http://www.yahoo.com/some/long/path/to/a/file">yahoo.com/some/long/pat..</a>"

//...

autolinker.link( "Go to www.google.com" );
// Produces: "Go to <a href="http://www.google.com">google.com</a>"

Retrieving the List of Matches

If you're just interested in retrieving the list of Matches without producing a transformed string, you can use the parse() method.

For example:

const matches = Autolinker.parse("Hello google.com, I am [email protected]", {
    urls: true,
    email: true
});

console.log(matches.length);         // 2
console.log(matches[0].type);        // 'url'
console.log(matches[0].getUrl());    // 'google.com'
console.log(matches[1].type);        // 'email'
console.log(matches[1].getEmail());  // '[email protected]'

Custom Replacement Function

A custom replacement function (replaceFn)
may be provided to replace url/email/phone/mention/hashtag matches on an
individual basis, based on the return from this function.

Full example, for purposes of documenting the API:

 const input = "...";  // string with URLs, Email Addresses, Mentions (Twitter, Instagram), and Hashtags

const linkedText = Autolinker.link(input, {
    replaceFn : function(match) {
        console.log("href = ", match.getAnchorHref());
        console.log("text = ", match.getAnchorText());

        switch(match.type) {
            case 'url':
                console.log("url: ", match.getUrl());

                return true;  // let Autolinker perform its normal anchor tag replacement

            case 'email':
                const email = match.getEmail();
                console.log("email: ", email);

                if(email === "[email protected]") {
                    return false;  // don't auto-link this particular email address; leave as-is
                } else {
                    return;  // no return value will have Autolinker perform its normal anchor tag replacement (same as returning `true`)
                }

            case 'phone':
                console.log("Phone Number: ", match.getPhoneNumber());

                return '<a href="http://newplace.to.link.phone.numbers.to/">' + match.getPhoneNumber() + '</a>';

            case 'mention':
                console.log("Mention: ", match.getMention());
                console.log("Mention Service Name: ", match.getServiceName());

                return '<a href="http://newplace.to.link.mention.handles.to/">' + match.getMention() + '</a>';

            case 'hashtag':
                console.log("Hashtag: ", match.getHashtag());

                return '<a href="http://newplace.to.link.hashtag.handles.to/">' + match.getHashtag() + '</a>';
        }
    }
} );

Modifying the default generated anchor tag

 const input = "...";  // string with URLs, Email Addresses, Mentions (Twitter, Instagram), and Hashtags

const linkedText = Autolinker.link( input, {
    replaceFn : function( match ) {
        console.log("href = ", match.getAnchorHref());
        console.log("text = ", match.getAnchorText());

        const tag = match.buildTag();       // returns an `Autolinker.HtmlTag` instance for an <a> tag
        tag.setAttr('rel', 'nofollow');   // adds a 'rel' attribute
        tag.addClass('external-link');    // adds a CSS class
        tag.setInnerHtml('Click here!');  // sets the inner html for the anchor tag

        return tag;
    }
} );

The replaceFn is provided one argument:

1. An Autolinker.match.Match
   object which details the match that is to be replaced.

A replacement of the match is made based on the return value of the function.
The following return values may be provided:

1. No return value (undefined), or true (boolean): Delegate back to
   Autolinker to replace the match as it normally would.
2. false (boolean): Do not replace the current match at all - leave as-is.
3. Any string: If a string is returned from the function, the string will be used
   directly as the replacement HTML for the match.
4. An Autolinker.HtmlTag
   instance, which can be used to build/modify an HTML tag before writing out its
   HTML text.

Full API Docs

The full API docs for Autolinker may be referenced at:
http://gregjacobs.github.io/Autolinker.js/api/

Live Example

http://gregjacobs.github.io/Autolinker.js/examples/

Upgrading from v3.x -> 4.x (Breaking Changes)

1. Internet Explorer support has been removed since its official demise in June
   2022.
2. The urls.wwwMatches config has been removed. A www. prefix is now treated
   like any other subdomain of a top level domain (TLD) match (such as
   'subdomain.google.com').
3. Match.getType() should be replaced with Match.type. This allows for
   TypeScript type narrowing of Match objects returned by the parse()
   method or inside the replaceFn.
4. The Matcher classes have been removed in favor of a single finite state
   machine parser, greatly improving the performance of Autolinker but removing
   some of the customizability of the old regular expressions. Will address this customizability in a future release.
5. Autolinker.AnchorTagBuilder, Autolinker.HtmlTag, and Autolinker.match.*
   references have been removed. These shouldn't be needed as public APIs, but
   please raise a GitHub issue if these are for some reason needed.

Upgrading from v2.x -> v3.x (Breaking Changes)

1. If you are still on v1.x, first follow the instructions in the
   Upgrading from v1.x -> v2.x
   section below.
2. The HtmlParser class has been removed in favor of an internal parseHtml()
   function which replaces the old regexp-based implementation with a state
   machine parser that is guaranteed to run in linear time. If you were using
   the HtmlParser class directly, I recommend switching to htmlparser2, which implements the HTML semantics
   better. The internal parseHtml() function that Autolinker now uses is
   fairly geared towards Autolinker's purposes, and may not be useful in a
   general HTML parsing sense.

Upgrading from v1.x -> v2.x (Breaking Changes)

1. If you are still on v0.x, first follow the instructions in the
   Upgrading from v0.x -> v1.x
   section below.

2. The codebase has been converted to TypeScript, and uses ES6 exports. You can
   now use the import statement to pull in the Autolinker class and related
   entities such as Match:

    // ES6/TypeScript/Webpack
   import Autolinker, { Match } from 'autolinker';
   

   The require() interface is still supported as well for Node.js:

    // Node.js
   const Autolinker = require('autolinker');
   

3. You will no longer need the @types/autolinker package as this package now
   exports its own types

4. You will no longer be able to override the regular expressions in the
   Matcher classes by assigning to the prototype (for instance, something like
   PhoneMatcher.prototype.regex = ...). This is due to how TypeScript creates
   properties for class instances in the constructor rather than on prototypes.

   The idea of providing your own regular expression for these classes is a
   brittle notion anyway, as the Matcher classes rely on capturing groups in
   the RegExp being in the right place, or even multiple capturing groups for
   the same piece of information to support a different format. These capturing
   groups and associated code are subject to change as the regular expression
   needs to be updated, and will not involve a major version release of
   Autolinker.

   In the future you will be able to override the default Matcher classes
   entirely to provide your own implementation, but please raise an issue (or
   +1 an issue) if you think the library should support a currently-unsupported
   format.

Upgrading from v0.x -> v1.x (Breaking Changes)

1. twitter option removed, replaced with mention (which accepts 'twitter',
   'instagram' and 'soundcloud' values)
2. Matching mentions (previously the twitter option) now defaults to
   being turned off. Previously, Twitter handle matching was on by
   default.
3. replaceFn option now called with just one argument: the Match
   object (previously was called with two arguments: autolinker and
   match)
4. (Used inside the replaceFn) TwitterMatch replaced with
   MentionMatch, and MentionMatch.getType() now returns 'mention'
   instead of 'twitter'
5. (Used inside the replaceFn) TwitterMatch.getTwitterHandle() ->
   MentionMatch.getMention()

Developing / Contributing

Pull requests definitely welcome. To setup the project, make
sure you have Node.js installed. Then
open up a command prompt and type the following:

cd Autolinker.js     # where you cloned the project
npm install

To run the tests:

npm run test

• Make sure to add tests to check your new functionality/bugfix
• Run the npm run test command to test

Building the Project Fully

For this you will need Ruby installed (note: Ruby
comes pre-installed on MacOS), with the JSDuck
gem.

See https://github.com/senchalabs/jsduck#getting-it for installation
instructions on Windows/Mac/Linux

JSDuck is used to build the project's
API/documentation site. See [Documentation Generator Notes](#Documentation Generator Notes)
for more info.

Running the Live Example Page Locally

Run:

yarn serve

Then open your browser to: http://localhost:8080/docs/examples/index.html

You should be able to make a change to source files, and refresh the page to see
the changes.

Note: If anyone wants to submit a PR converting gulp watch to webpack with
the live development server, that would be much appreciated :)

Documentation Generator Notes

This project uses JSDuck for its
documentation generation, which produces the page at http://gregjacobs.github.io/Autolinker.js.

Unfortunately, JSDuck is a very old project that is no longer maintained. As
such, it doesn't support TypeScript or anything from ES6 (the class keyword,
arrow functions, etc). However, I have yet to find a better documentation
generator that creates such a useful API site. (Suggestions for a new one are
welcome though - please raise an issue.)

Since ES6 is not supported, we must generate the documentation from the ES5
output. As such, a few precautions must be taken care of to make sure the
documentation comes out right:

1. @cfg documentation tags must exist above a class property that has a
   default value, or else it won't end up in the ES5 output. For example:

    // Will correctly end up in the ES5 output
   
   /**
    * @cfg {String} title
    */
   readonly title: string = '';
   
   
   
   // Will *not* end up in ES5 output, and thus, won't end up in the generated
   // documentation
   
   /**
    * @cfg {String} title
    */
   readonly title: string;
   

2. The @constructor tag must be replaced with @method constructor

Changelog

See Releases