npm package: @onachi/html2pdf.js
Description: Client-side HTML-to-PDF rendering using pure JS
Author: Erik Koopmans
Latest version: 0.10.3

# html2pdf.js

html2pdf.js converts any webpage or element into a printable PDF entirely client-side using [html2canvas](https://github.com/niklasvh/html2canvas) and [jsPDF](https://github.com/MrRio/jsPDF).

> :warning: There have been several issues reported in v0.10. They are being investigated but in the meantime you may wish to remain on v0.9.3 ("^0.9.3" in npm, or [use cdnjs for HTML script tags](https://cdnjs.com/libraries/html2pdf.js/0.9.3)).

## Table of contents

- [html2pdf.js](#html2pdfjs)
  - [Table of contents](#table-of-contents)
  - [Getting started](#getting-started)
      - [CDN](#cdn)
      - [Raw JS](#raw-js)
      - [NPM](#npm)
      - [Bower](#bower)
      - [Console](#console)
  - [Usage](#usage)
    - [Advanced usage](#advanced-usage)
      - [Workflow](#workflow)
      - [Worker API](#worker-api)
  - [Options](#options)
    - [Page-breaks](#page-breaks)
      - [Page-break settings](#page-break-settings)
      - [Page-break modes](#page-break-modes)
      - [Example usage](#example-usage)
    - [Image type and quality](#image-type-and-quality)
  - [Progress tracking](#progress-tracking)
  - [Dependencies](#dependencies)
  - [Contributing](#contributing)
    - [Issues](#issues)
      - [Known issues](#known-issues)
    - [Tests](#tests)
    - [Pull requests](#pull-requests)
  - [Credits](#credits)
      - [Contributors](#contributors)
      - [Special thanks](#special-thanks)
  - [License](#license)

## Getting started

#### CDN

The simplest way to use html2pdf.js is to include it as a script in your HTML by using cdnjs:

```html
<script src="https://cdnjs.cloudflare.com/ajax/libs/html2pdf.js/0.10.1/html2pdf.bundle.min.js" integrity="sha512-GsLlZN/3F2ErC5ifS5QtgpiJtWd43JWSuIgh7mbzZ8zBps+dvLusV+eNQATqgA/HdeKFVgA5v3S/cIrLF7QnIg==" crossorigin="anonymous" referrerpolicy="no-referrer"></script>
```

Using a CDN URL will lock you to a specific version, which should ensure stability and give you control over when to change versions. cdnjs gives you access to [all past versions of html2pdf.js](https://cdnjs.com/libraries/html2pdf.js).

*Note: [Read about dependences](#dependencies) for more information about using the unbundled version `dist/html2canvas.min.js`.*

#### Raw JS

 You may also download `dist/html2pdf.bundle.min.js` directly to your project folder and include it in your HTML with:

```html
<script src="html2pdf.bundle.min.js"></script>
```

#### 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](https://webmasters.stackexchange.com/a/77337/94367)).
2. Paste in this code:
    ```js
    function addScript(url) {
        var script = document.createElement('script');
        script.type = 'application/javascript';
        script.src = url;
        document.head.appendChild(script);
    }
    addScript('https://cdnjs.cloudflare.com/ajax/libs/html2pdf.js/0.10.1/html2pdf.bundle.min.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:

```js
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:

```js
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:

```js
// 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](https://rawgit.com/MrRio/jsPDF/master/docs/jspdf.js.html#line992) 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](#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](#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:

```js
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](#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](#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](https://html2canvas.hertzen.com/configuration) for usage).|
|jsPDF       |object          |`{ }`                           |Configuration options sent directly to `jsPDF` ([see here](http://rawgit.com/MrRio/jsPDF/master/docs/jsPDF.html) for usage).|
|beforeAddImage       |(jsPDF: jsPDF, options: Options) => BeforeAddImageOptions          |undefined                          |call this function before `(new jsPDF()).addImage()`|


```typescript
interface BeforeAddImageOptions {
  /** html2pdf.js's opt */
  opt: Object;
  /** now page number */
  page: number;
  /** created by canvas.toDataURL */
  imgData: string;
  /** pageSize */
  pageSize: {
    width: number;
    height: number;
  }
}
```
### 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`](https://developer.mozilla.org/en-US/docs/Web/CSS/break-before), [`break-after`](https://developer.mozilla.org/en-US/docs/Web/CSS/break-after), and [`break-inside`](https://developer.mozilla.org/en-US/docs/Web/CSS/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

```js
// 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()](https://developer.mozilla.org/en-US/docs/Web/API/HTMLCanvasElement/toDataURL), which ignores quality settings for 'png' images. To enable png image compression, try using the [canvas-png-compression shim](https://github.com/ShyykoSerhiy/canvas-png-compression), 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](https://github.com/niklasvh/html2canvas), [jsPDF](https://github.com/MrRio/jsPDF), and [es6-promise](https://github.com/stefanpenner/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:

```html
<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](https://jsfiddle.net/u6o6ne41/) (which has html2pdf.js already loaded). Remember that html2pdf.js uses [html2canvas](https://github.com/niklasvh/html2canvas) and [jsPDF](https://github.com/MrRio/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](https://jsfiddle.net/eKoopmans/z1rupL4c/), 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:
    - direct file: Go to [html2pdf.js/bugfix/clone-nodes-BUILD](/eKoopmans/html2pdf.js/tree/bugfix/clone-nodes-BUILD) and replace the files in your project with the relevant files (e.g. `dist/html2pdf.bundle.js`)
    - npm: `npm install eKoopmans/html2pdf.js#bugfix/clone-nodes-BUILD`
    - Related project: [Bugfix: Cloned nodes](https://github.com/eKoopmans/html2pdf.js/projects/9)

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](https://github.com/eKoopmans/html2pdf.js/projects/1)

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](https://github.com/eKoopmans/html2pdf.js/projects/4)

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](https://github.com/eKoopmans/html2pdf.js/projects/11)

6. **Maximum size:** HTML5 canvases have a [maximum height/width](https://stackoverflow.com/a/11585939/4080966). 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](https://github.com/eKoopmans/html2pdf.js/projects/5)

### 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](https://github.com/eKoopmans)

#### Contributors

- [@WilcoBreedt](https://github.com/WilcoBreedt)
- [@Ranger1230](https://github.com/Ranger1230)

#### Special thanks

- [Sauce Labs](https://saucelabs.com/) for unit testing.

## License

[The MIT License](http://opensource.org/licenses/MIT)

Copyright (c) 2017-2019 Erik Koopmans <[http://www.erik-koopmans.com/](http://www.erik-koopmans.com/)>