Europa Worker is a library for converting HTML into valid Markdown within a worker.

cheerio is used to parse HTML input without the need for complexity.

• Install
• Examples
• API
• Plugins
• Bugs
• Contributors
• License

Install

Install using your preferred package manager. For example;

$ npm install --save europa-worker

Check out europa, node-europa, or europa-cli if you want to install it for use within a web browser, Node.js, or as a CLI respectively.

Examples

const europa = new Europa();

europa.convert('<a href="https://github.com/neocotic/europa">Europa</a>');

API

Simply create an instance of Europa and you've done most of the work. You can control many aspects of the HTML to Markdown conversion by passing the following options to the constructor:

| Option | Type | Description | Default | |------------|---------|-------------------------------------------------------------------------------------|---------------------------| | absolute | Boolean | Whether absolute URLs should be used for elements (e.g. anchors, images) | false | | baseUri | String | The base URI used to resolve relative URLs used for elements (e.g. anchors, images) | Parent of location.href | | eol | String | The end of line character to be inserted into generated Markdown | "\n" | | inline | Boolean | Whether URLs for elements (e.g. anchors, images) are to be inserted inline | false |

const europa = new Europa({
  absolute: true,
  baseUri: 'https://example.com',
  eol: '\r\n',
  inline: true,
});

convert(input)

Converts the specified input into Markdown.

input can either be an HTML string or DOM node(s) to be converted into Markdown. For a DOM node to be converted, it must be compatible with the AnyNode type as declared in the domhandler package to ensure that it works. This can be easily done using cheerio, which helps power Europa Worker under-the-hood.

const europa = new Europa();

europa.convert('<blockquote><b>Europa</b> is great!</blockquote>');
//=> "> **Europa** is great!"
europa.convert($('.lead')[0]);
//=> "_Everyone_ ♥ **Europa**!"

europa.convert($('<div>').html('Please keep my <span style="display: none">treasure</span> secret safe...')[0]);
//=> "Please keep my secret safe..."

Plugins

Europa is fully pluggable and is packed with default plugins in order to get full support for basic Markdown. It enables the creation of external plugins to further extend Europa's capabilities to support extended Markdown syntax or even new HTML elements should they not be added to Europa quick enough for you.

Plugins are packaged independently, however, the default plugins are included in europa-preset-default and is bundled with Europa Core so that they are available to all implementations with no extra effort.

The API for plugins is simple on a high level, but you'll need to get to grips with the internal API to understand what you can really do:

import { Plugin, PluginApi } from 'europa-core';
import Europa from 'europa-worker';

const examplePluginProvider = (api: PluginApi): Plugin => ({
  // All fields and methods are optional
  converters: {
    TAGNAME: {
      startTag(conversion, context): boolean { /* ... */ },
      endTag(conversion, context) { /* ... */ },
    },
  },
  convertText(value, conversion): boolean { /* ... */ },
  startConversion(conversion) { /* ... */ },
  endConversion(conversion) { /* ... */ },
});

Europa.registerPlugin(examplePluginProvider);

It's highly recommended to look at existing plugins to get a better understanding of how things work.

Since multiple plugins could support the same tag(s), the load order is important as the last plugin loaded that declares support for a tag, will be the one that's used. Be wary of overriding tags supported by default plugins and consider whether it's something that should be part of the original plugin. If so, open a pull request!

A good practice for naming plugin packages is europa-plugin-<markdown-feature>. For example; europa-plugin-link and not europa-plugin-a, and europa-plugin-quote and not europa-plugin-q. Each plugin should aim to support a specific Markdown feature.

Take a look at Europa Build to quickly generate a Europa plugin package.

Presets

Europa also has the concept of a "preset", which is essentially a bundle of plugins. In fact, all the default plugins are provided by a default preset.

A preset simply imports a collection of plugins and declares them so that they can be registered together. For example;

import { PluginApi, PluginProvider, Preset } from 'europa-core';
import examplePluginProvider from 'europa-plugin-example';
import Europa from 'europa-worker';

const pluginProviders: PluginProvider[] = [
  examplePluginProvider,
  // ...
];

const examplePresetProvider = (api: PluginApi): Preset => ({
  // All fields and methods are optional
  plugins: pluginProviders.map((pluginProvider) => pluginProvider(api)),
});

Europa.registerPreset(examplePresetProvider);

A good practice for naming preset packages is europa-preset-<markdown-feature-set>. For example; europa-preset-github could be used to register plugins that converts HTML to GitHub-flavoured Markdown. Each preset should include plugins that aim to support a related Markdown feature set.

Take a look at Europa Build to quickly generate a Europa preset package.

Bugs

If you have any problems with Europa Worker or would like to see changes currently in development you can do so here.

Contributors

If you want to contribute, you're a legend! Information on how you can do so can be found in CONTRIBUTING.md. We want your suggestions and pull requests!

A list of Europa contributors can be found in AUTHORS.md.

License

Copyright © 2022 neocotic

See LICENSE.md for more information on our MIT license.