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nodepub

2.0.7 • Public • Published

Nodepub v2.0.7

Create valid EPUB (v2) ebooks with metadata, contents and cover image.

By K Cartlidge.

Licence

MIT Licence (very permissive). See the GitHub licence summary bullet points here.

A copy of the licence is within the package source.

About Nodepub

Nodepub is a Node module which can be used to create EPUB (v2) documents.

The resultant files are designed to pass the IDPF online validator and Sigil's preflight checks. They also open fine in IBooks, Adobe Digital Editions and Calibre, plus the Kobo H20 ereader (a highly recommended backlit and waterproof e-ink device).

They also pass KindleGen - although Amazon's .mobi files do not support the cover page HTML file the KindleGen tool strips it out so there is no need to make special allowance.

Recent Changes

  • v2.0.7 - Thanks to Harold Treen the API has switched to being asynchronous. See the examples below for the usage of the callbacks.

  • v1.0.7 - This version introduces stability at the expense of minor breaking changes, consisting almost entirely of renames from chapter to section but with some of the pre-generated pages of earlier versions eliminated. The result is more abstracted but also more flexible, whilst also retaining most of it's simplicity.

Notes on the EPUBs

Resultant EPUBs can be generated to one of three levels of completeness:

  1. Either a complete .epub file ready for distribution
  2. Or a folder containing all the files necessary to build the final EPUB
  3. Or a Javascript object containing all the filenames and content needed for the final EPUB

The module has no concept of how the original content is obtained; it is passed a metadata object at creation after which content is added sequentially by the caller. There is no automatic pre-processing of content files such as Markdown as the module expects to be given HTML to work with and it is trivial for the caller to pre-process in advance by requiring a Markdown module, the Jade rendering engine or similar.

Current Status

  • The generation of EPUBs to all three levels of completeness mentioned above is in place along with an example script to show the usage. The codebase also includes the resulting example EPUB.

  • EPUBs generated pass the expectations listed above.

  • All tests pass.

  • Cover images are included (must be in PNG format). I recommend 600x800 or a larger alternative of the same aspect ratio.

  • Custom CSS can be provided.

  • NEW - Inline images within the EPUB.

  • NEW - There is now an option to provide a callback function for the generation of the HTML contents page. See the Public Methods area below for more details.

  • Sections can appear as front matter, before the contents page.

  • Sections can optionally be excluded from the pre-generated contents page and metadata-based navigation.

  • NEW - OEBPS and suitable subfolders now created within the EPUB (not actually required by the spec other than for the mimetype but there is a certain expectation regarding internal folder structure).

If you use the raw generated files to write the EPUB yourself, bear in mind that the mimetype file MUST be the first file in the archive and also MUST NOT be compressed. In simple terms, an EPUB is a renamed ZIP file where compression is optional apart from the mimetype file which should be added first using the 'store' option.

Upcoming

  • Other non-image assets. You already have images so the base functionality is there, but I will be adding an option to include other assets (for example an embedded font).

Requirements

It's an NPM module and depends upon a couple of (mainstream) packages. No external dependencies.

Installation

It's an npm module:

npm install --save nodepub

The --save bit is optional, but will update your dependencies.

Tests and Example

To run the tests, in the top folder (containing the package.json file) run the following and check the inner test subfolder for a resulting final EPUB:

npm test

Important Note about the Tests

The tests mostly stub fs where used. However at one point they do actually write a final EPUB document as this also serves as one example of the resulting files.

This means that (a) the test process needs write access to the test folder and (b) an actual file is generated. Whilst the process is tested, the final EPUB is not; I have manually tested it via the IDPF Validator. The actual testing of an EPUB file is already sufficiently covered by the epubcheck tool which that site uses, and I have not added it as an integration test.

In addition an example.js script is provided:

cd example
node example.js
cd ..

This generates a more complete example EPUB document than the test, and the code is commented.

Usage

You may find it easier just to look at the example.js file aforementioned.

For viewing generated metadata I recommend opening the EPUB in Sigil and using it's Tools, Metadata option (F8).

Using nodepub is straightforward. The HTML you provide for chapter contents should be the body markup only (typically a sequence of <p>one paragraph of text</p> lines or headers).

The steps are:

  • Require the module and call document() with a metadata object detailing your book plus the path of a cover image:
var epub = makepub.document(metadata, "cover.png");
  • Optionally add some CSS definitions:
epub.addCSS(myCSS);
  • Repeatedly call addSection() with a title and HTML contents, plus options for whether to exclude from the contents list and/or use as front matter:
epub.addSection('Chapter 1', "<h1>One</h1><p>...</p>");
  • Produce one of the following outputs:

    • Call getFilesForEPUB() if you want a simple array of file description and contents for storing in a database or further working through. This array will contain all needed files for a valid EPUB, along with their name, subfolder (if any) and a flag as to whether they should be compressed (a value of false should not be ignored).

    • Call writeFilesForEPUB() if you want to create a folder containing the complete files as mentioned above. You can edit these and produce an EPUB; simply zip the files and change the extention. For a valid EPUB the mimetype file must be added first and must not be compressed. Some validators will pass the file anyway; some ereaders will fail to read it.

    • Call writeEPUB(). This is the easiest way and also the only one guaranteed to produce valid EPUB output simply because the other two methods allow for changes and compression issues.

Public Methods

The following assumes the module has been required using the following statement:

var makepub = require("nodepub");

document ( metadata, coverImage, generateContentsCallback )

This begins a new document with the given metadata (see below) and cover image (a path to a PNG).

Custom Table of Contents

If the generateContentsCallback function is provided then when the HTML markup for a table of contents is needed this function will be called. It will be given 2 parameters; an array of link objects for the contents page and the pre-generated markup in case you want to just amend the default version rather than take full responsibility for it.

Simple Example (Default TOC):

var epub = makepub.document(metadata, "./cover.png");

Callback Example (Default TOC) 1:

var makeContents = function(links, defaultMarkup) {
    return defaultMarkup.toUppercase();
};
var epub = makepub.document(metadata, "./cover.png", makeContents);

Callback Example (Custom TOC) 2:

var makeContents = function(links, defaultMarkup) {
    var contents = "<h1>Chapters</h1>";
    _.each(links, function (link) {
        if (link.itemType !== "contents") {
            contents += "<a href='" + link.link + "'>" + link.title + "</a><br />";
        }
    });
    return contents;
};
var epub = makepub.document(metadata, "./cover.png", makeContents);

Callback Example (Custom TOC) 3:

This one is from Harold Treen who raised a pull request which turned out to be unnecessary (my fault) because I wasn't clear enough about the purpose of this callback (I've adjusted the text above the examples to clarify this aspect; apologies).

function makeToc(links) {
        const tableOfContents = ['<h2>Table Of Contents</h2>', '<ol class="toc-items">'];
 
        links.forEach((link) => {
            if (link.itemType === 'main') {
                tableOfContents.push(`<li><a href="${link.link}">${link.title}</a></li>`);
            }
        });
 
        tableOfContents.push('</ol>');
 
        return tableOfContents.join('\n');
}
 
const document = nodepub.document(metadata, coverPath, makeToc);

The links array which is passed to a callback consists of objects with the following properties:

  • title - the title of the section to be linked to.
  • link - the relative href within the EPUB.
  • itemType - one of 3 types, those being front for front matter, contents for the contents page and main for the remaining sections.

The callback should return a string of HTML which will be placed between the body and /body tags on the contents page.


addCSS ( content )

Adds your own custom CSS entries for use across all pages in the ebook. The default CSS is empty.

Example:

epub.addCSS("body { font-size: 14pt; }");

addSection ( title, content, excludeFromContents, isFrontMatter )

Adds a section, which is usually something like a front matter page, a copyright page, a chapter or an about the author page.

  • title, content - these parameters are obvious.
  • excludeFromContents - this option (default false) allows you to add content which does not appear either in the auto-generated HTML table of contents or the metadata contents used directly by ereaders/software. This is handy for example when adding a page just after the cover containing the title and author - quite a common page which does not usually warrant it's own contents entry.
  • isFrontMatter - this option (default false) specifies that the section should appear before the contents page. This is often used for copyright pages or similar.

Example:

epub.addSection('Copyright', myCopyrightText, false, true);
epub.addSection('Chapter 1', "<h1>One</h1><p>...</p>");

getSectionCount ( )

Returns the quantity of sections currently added.

Example:

var qty = epub.getSectionCount();

getFilesForEPUB (callback)

Invokes callback with an array of objects for the files needed to create an EPUB as defined so far. Writing these files in the sequence given and respecting all the properties provided should give a valid EPUB document.

Example:

epub.getFilesForEPUB(function(err, files) {
    console.log("Files needed:", files.length);
});

Each entry has the following properties:

  • name - the filename within the EPUB archive.
  • folder - any folder within the EPUB archive within which the file should be placed.
  • compress - whether the file should be compressed - for a fully compliant EPUB this must be respected as it is a requirement for the mimetype (which will also be listed [and must be written] first).
  • content - the raw content to write.

writeFilesForEPUB ( folder, callback )

Creates the folder (if need be) then writes the files/folders in the order returned by getFilesForEPUB. This is ideal for debugging purposes or if you intend to manually/programmatically make changes.

Note that if you are creating your own EPUB from this set of files it is your own responsibility to ensure that the mimetype file appears first and is uncompressed (technically meaning stored).

Example:

var qty = epub.writeFilesForEPUB("./raw-files", function(err) {
    if (!err) {
        console.log('Files written!');
    }
});

writeEPUB ( onError, folder, filename, onSuccess )

Creates a version 2 EPUB document.

  • onError - an optional callback function (or null) which will be given a single parameter representing any exception raised.
  • folder - the location to write the EPUB.
  • filename - the name of the resulting EPUB file without the extention.
  • onSuccess - an optional callback function (or null) which will be actioned upon document generation completion.

Example:

epub.writeEPUB(function (e) {
    console.log("Error:", e);
}, './output', 'example-ebook', function () {
    console.log("EPUB created.")
});

Metadata

The metadata object passed into the document method should look like this:

var metadata = {
    id: Date.now(),
    title: 'Unnamed Document',
    series: 'My Series',
    sequence: 1,
    author: 'Anonymous',
    fileAs: 'Anonymous',
    genre: 'Non-Fiction',
    tags: 'Sample,Example,Test',
    copyright: 'Anonymous, 1980',
    publisher: 'My Fake Publisher',
    published: '2000-12-31',
    language: 'en',
    description: 'A test book.',
    contents: 'Chapters',
    source: 'http://www.kcartlidge.com',
    images: ["../test/hat.png"]
};

The properties are:

  • id - the book ID, whether that be an ISBN, an Amazon product code or just a random string.
  • title - just the book title; do not append details of any series or sequence.
  • series - any series to which the book belongs (e.g. The Fellowship of the Ring belongs to the series The Lord of the Rings).
  • sequence - the book number within any series (e.g. 1 in the Lord of the Rings example above).
  • author - the user-friendly author name (e.g. K Cartlidge).
  • fileAs - how the author should be considered when filing/sorting (e.g. Cartlidge, K).
  • genre - anything you like (e.g. Science Fiction).
  • tags - a comma-delimited list of keyword-style tags, which will appear as multiple subjects in the EPUB.
  • copyright - how you want the copyright to appear when applied as a substitution (see below), without the © symbol.
  • publisher - the name of the publisher (or yourself if none).
  • published - the publication date (note the year/month/day format).
  • language - the short ISO language name (e.g. en for English or fr for French).
  • description - the short description included within the book definition and shown in (for example) the list view in iBooks.
  • contents - the title of the auto-generated contents HTML page.
  • source - the derivation of the document, in this case a URL but it could also be an ISBN or similar if it is a derivative work.
  • images - embedded images for the document - specify them here as proper paths, and within the document markup href link to them as a file within a (flat) parent images folder. For example ~/Documents/book/images/hat.png in the matadata whould then be linked to in the HTML as ../images/hat.png.

Substitutions

As mentioned briefly under the copyright entry of the metadata section above, a form of text substitution is supported.

Basically, at any point in your section content you may include placeholders like [[COPYRIGHT]]. When the EPUB is generated any such placeholders which (within the double square braces) match the capitalised name of a metadata entry are replaced with the corresponding metadata value.

For example, you could have a Thanks for Reading page at the end of your book which has the following markup:

<p>Thanks for reading <strong>[[TITLE]]</strong> by <em>[[AUTHOR]]</em>.</p>

When the EPUB is produced and opened it will then look like:


Thanks for reading The Hobbit by JRR Tolkien.


This means you can re-use snippets of content across multiple books or refer to the author/title/series/whatever at any point within the book without worrying about consistency of spelling, naming conventions etcetera.

Reminder

This is a utility module, not a user-facing one. In other words it is assumed that the caller has already validated the inputs. Only basic ommission checks are performed

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