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@tn1027/html2pdf.js

0.0.3 • Public • Published

html2pdf.js

html2pdf.js converts any webpage or element into a printable PDF entirely client-side using html2canvas and jsPDF.

Table of contents

Getting started

HTML

The simplest way to use html2pdf.js is to download dist/html2pdf.bundle.min.js to your project folder and include it in your HTML with:

<script src="html2pdf.bundle.min.js"></script>

Note: Click here for more information about using the unbundled version dist/html2canvas.min.js.

NPM

Install html2pdf.js and its dependencies using NPM with npm install --save html2pdf.js (make sure to include .js in the package name).

Note: You can use NPM to create your project, but html2pdf.js will not run in Node.js, it must be run in a browser.

Bower

Install html2pdf.js and its dependencies using Bower with bower install --save html2pdf.js (make sure to include .js in the package name).

Console

If you're on a webpage that you can't modify directly and wish to use html2pdf.js to capture a screenshot, you can follow these steps:

  1. Open your browser's console (instructions for different browsers here).
  2. Paste in this code: 
    function addScript(url) {
    var script = document.createElement('script');
    script.type = 'application/javascript';
    script.src = url;
    document.head.appendChild(script);
}
addScript('https://raw.githack.com/eKoopmans/html2pdf/master/dist/html2pdf.bundle.js');
  3. You may now execute html2pdf.js commands directly from the console. To capture a default PDF of the entire page, use html2pdf(document.body).

Usage

Once installed, html2pdf.js is ready to use. The following command will generate a PDF of #element-to-print and prompt the user to save the result:

var element = document.getElementById('element-to-print');
html2pdf(element);

Advanced usage

Every step of html2pdf.js is configurable, using its new Promise-based API. If html2pdf.js is called without arguments, it will return a Worker object:

var worker = html2pdf();  // Or:  var worker = new html2pdf.Worker;

This worker has methods that can be chained sequentially, as each Promise resolves, and allows insertion of your own intermediate functions between steps. A prerequisite system allows you to skip over mandatory steps (like canvas creation) without any trouble:

// This will implicitly create the canvas and PDF objects before saving.
var worker = html2pdf().from(element).save();

Workflow

The basic workflow of html2pdf.js tasks (enforced by the prereq system) is:

.from() -> .toContainer() -> .toCanvas() -> .toImg() -> .toPdf() -> .save()

Worker API

Method Arguments Description
from src, type Sets the source (HTML string or element) for the PDF. Optional type specifies other sources: 'string', 'element', 'canvas', or 'img'.
to target Converts the source to the specified target ('container', 'canvas', 'img', or 'pdf'). Each target also has its own toX method that can be called directly: toContainer(), toCanvas(), toImg(), and toPdf().
output type, options, src Routes to the appropriate outputPdf or outputImg method based on specified src ('pdf' (default) or 'img').
outputPdf type, options Sends type and options to the jsPDF object's output method, and returns the result as a Promise (use .then to access). See the jsPDF source code for more info.
outputImg type, options Returns the specified data type for the image as a Promise (use .then to access). Supported types: 'img', 'datauristring'/'dataurlstring', and 'datauri'/'dataurl'.
save filename Saves the PDF object with the optional filename (creates user download prompt).
set opt Sets the specified properties. See Options below for more details.
get key, cbk Returns the property specified in key, either as a Promise (use .then to access), or by calling cbk if provided.
then onFulfilled, onRejected Standard Promise method, with this re-bound to the Worker, and with added progress-tracking (see Progress below). Note that .then returns a Worker, which is a subclass of Promise.
thenCore onFulFilled, onRejected Standard Promise method, with this re-bound to the Worker (no progress-tracking). Note that .thenCore returns a Worker, which is a subclass of Promise.
thenExternal onFulfilled, onRejected True Promise method. Using this 'exits' the Worker chain - you will not be able to continue chaining Worker methods after .thenExternal.
catch, catchExternal onRejected Standard Promise method. catchExternal exits the Worker chain - you will not be able to continue chaining Worker methods after .catchExternal.
error msg Throws an error in the Worker's Promise chain.

A few aliases are also provided for convenience:

Method Alias
save saveAs
set using
output export
then run

Options

html2pdf.js can be configured using an optional opt parameter:

var element = document.getElementById('element-to-print');
var opt = {
  margin:       1,
  filename:     'myfile.pdf',
  image:        { type: 'jpeg', quality: 0.98 },
  html2canvas:  { scale: 2 },
  jsPDF:        { unit: 'in', format: 'letter', orientation: 'portrait' }
};

// New Promise-based usage:
html2pdf().set(opt).from(element).save();

// Old monolithic-style usage:
html2pdf(element, opt);

The opt parameter has the following optional fields:

Name Type Default Description
margin number or array 0 PDF margin (in jsPDF units). Can be a single number, [vMargin, hMargin], or [top, left, bottom, right].
filename string 'file.pdf' The default filename of the exported PDF.
pagebreak object {mode: ['css', 'legacy']} Controls the pagebreak behaviour on the page. See Page-breaks below.
image object {type: 'jpeg', quality: 0.95} The image type and quality used to generate the PDF. See Image type and quality below.
enableLinks boolean true If enabled, PDF hyperlinks are automatically added ontop of all anchor tags.
html2canvas object { } Configuration options sent directly to html2canvas (see here for usage).
jsPDF object { } Configuration options sent directly to jsPDF (see here for usage).

Page-breaks

html2pdf.js has the ability to automatically add page-breaks to clean up your document. Page-breaks can be added by CSS styles, set on individual elements using selectors, or avoided from breaking inside all elements (avoid-all mode).

By default, html2pdf.js will respect most CSS break-before, break-after, and break-inside rules, and also add page-breaks after any element with class html2pdf__page-break (for legacy purposes).

Page-break settings

Setting Type Default Description
mode string or array ['css', 'legacy'] The mode(s) on which to automatically add page-breaks. One or more of 'avoid-all', 'css', and 'legacy'.
before string or array [] CSS selectors for which to add page-breaks before each element. Can be a specific element with an ID ('#myID'), all elements of a type (e.g. 'img'), all of a class ('.myClass'), or even '*' to match every element.
after string or array [] Like 'before', but adds a page-break immediately after the element.
avoid string or array [] Like 'before', but avoids page-breaks on these elements. You can enable this feature on every element using the 'avoid-all' mode.

Page-break modes

Mode Description
avoid-all Automatically adds page-breaks to avoid splitting any elements across pages.
css Adds page-breaks according to the CSS break-before, break-after, and break-inside properties. Only recognizes always/left/right for before/after, and avoid for inside.
legacy Adds page-breaks after elements with class html2pdf__page-break. This feature may be removed in the future.

Example usage

// Avoid page-breaks on all elements, and add one before #page2el.
html2pdf().set({
  pagebreak: { mode: 'avoid-all', before: '#page2el' }
});

// Enable all 'modes', with no explicit elements.
html2pdf().set({
  pagebreak: { mode: ['avoid-all', 'css', 'legacy'] }
});

// No modes, only explicit elements.
html2pdf().set({
  pagebreak: { before: '.beforeClass', after: ['#after1', '#after2'], avoid: 'img' }
});

Image type and quality

You may customize the image type and quality exported from the canvas by setting the image option. This must be an object with the following fields:

Name Type Default Description
type string 'jpeg' The image type. HTMLCanvasElement only supports 'png', 'jpeg', and 'webp' (on Chrome).
quality number 0.95 The image quality, from 0 to 1. This setting is only used for jpeg/webp (not png).

These options are limited to the available settings for HTMLCanvasElement.toDataURL(), which ignores quality settings for 'png' images. To enable png image compression, try using the canvas-png-compression shim, which should be an in-place solution to enable png compression via the quality option.

Progress tracking

The Worker object returned by html2pdf() has a built-in progress-tracking mechanism. It will be updated to allow a progress callback that will be called with each update, however it is currently a work-in-progress.

Dependencies

html2pdf.js depends on the external packages html2canvas, jsPDF, and es6-promise. These dependencies are automatically loaded when using NPM or the bundled package.

If using the unbundled dist/html2pdf.min.js (or its un-minified version), you must also include each dependency. Order is important, otherwise html2canvas will be overridden by jsPDF's own internal implementation:

<script src="es6-promise.auto.min.js"></script>
<script src="jspdf.min.js"></script>
<script src="html2canvas.min.js"></script>
<script src="html2pdf.min.js"></script>

Contributing

Issues

When submitting an issue, please provide reproducible code that highlights the issue, preferably by creating a fork of this template jsFiddle (which has html2pdf.js already loaded). Remember that html2pdf.js uses html2canvas and jsPDF as dependencies, so it's a good idea to check each of those repositories' issue trackers to see if your problem has already been addressed.

Known issues

  1. Rendering: The rendering engine html2canvas isn't perfect (though it's pretty good!). If html2canvas isn't rendering your content correctly, I can't fix it.

    • You can test this with something like this fiddle, to see if there's a problem in the canvas creation itself.

  2. Node cloning (CSS etc): The way html2pdf.js clones your content before sending to html2canvas is buggy. A fix is currently being developed - try out:

  3. Resizing: Currently, html2pdf.js resizes the root element to fit onto a PDF page (causing internal content to "reflow").

    • This is often desired behaviour, but not always.
    • There are plans to add alternate behaviour (e.g. "shrink-to-page"), but nothing that's ready to test yet.
    • Related project: Feature: Single-page PDFs

  4. Rendered as image: html2pdf.js renders all content into an image, then places that image into a PDF.

    • This means text is not selectable or searchable, and causes large file sizes.
    • This is currently unavoidable, however recent improvements in jsPDF mean that it may soon be possible to render straight into vector graphics.
    • Related project: Feature: New renderer

  5. Promise clashes: html2pdf.js relies on specific Promise behaviour, and can fail when used with custom Promise libraries.

    • In the next release, Promises will be sandboxed in html2pdf.js to remove this issue.
    • Related project: Bugfix: Sandboxed promises

  6. Maximum size: HTML5 canvases have a maximum height/width. Anything larger will fail to render.

    • This is a limitation of HTML5 itself, and results in large PDFs rendering completely blank in html2pdf.js.
    • The jsPDF canvas renderer (mentioned in Known Issue #4) may be able to fix this issue!
    • Related project: Bugfix: Maximum canvas size

Tests

html2pdf.js is currently sorely lacking in unit tests. Any contributions or suggestions of automated (or manual) tests are welcome. This is high on the to-do list for this project.

Pull requests

If you want to create a new feature or bugfix, please feel free to fork and submit a pull request! Create a fork, branch off of master, and make changes to the /src/ files (rather than directly to /dist/). You can test your changes by rebuilding with npm run build.

Credits

Erik Koopmans

Contributors

Special thanks

License

The MIT License

Copyright (c) 2017-2019 Erik Koopmans <http://www.erik-koopmans.com/>

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