html-to-pdfmake

html-to-pdfmake

pdfmake permits to easily create a PDF with JavaScript, but the support of HTML was missing. After reviewing issue #205 I decided to create a module to handle this feature.

Online Demo

You can find the online demo at https://aymkdn.github.io/html-to-pdfmake/index.html

Install

npm install html-to-pdfmake

How to use

This module will convert some basic and valid HTML code to its equivalent in pdfmake.

var pdfMake = require("pdfmake/build/pdfmake");
var pdfFonts = require("pdfmake/build/vfs_fonts");
pdfMake.vfs = pdfFonts.pdfMake.vfs;
var htmlToPdfmake = require("html-to-pdfmake");
// or:
// import htmlToPdfmake from "html-to-pdfmake"
// or, if used directly in a web browser:
// <script src="https://cdn.jsdelivr.net/npm/html-to-pdfmake/docs/browser.js"></scrpipt>

var html = htmlToPdfmake(`
  <div>
    <h1>My title</h1>
    <p>
      This is a sentence with a <strong>bold word</strong>, <em>one in italic</em>,
      and <u>one with underline</u>. And finally <a href="https://www.somewhere.com">a link</a>.
    </p>
  </div>
`);

/*
it will return:
{
  stack:[
    {
      text: 'My title',
      fontSize: 24,
      bold: true,
      marginBottom: 5,
      style: ['html-h1']
    },
    {
      text: [
        {
          text: 'This is a sentence with a '
        },
        {
          text: 'bold word',
          bold: true,
          style: ['html-strong']
        },
        {
          text: ', '
        },
        {
          text: 'one in italic',
          italics: true,
          style: ['html-em']
        },
        {
          text: ', and '
        },
        {
          text: 'one with underline',
          decoration: 'underline',
          style: ['html-u']
        },
        {
          text: '. And finally '
        },
        {
          text: 'a link',
          color: 'blue',
          decoration: 'underline',
          link: 'https://www.somewhere.com',
          style: ['html-a']
        },
        {
          text: '.'
        }
      ],
      margin: [0, 5, 0, 10],
      style: ['html-p']
    }
  ],
  style: ['html-div']
}
 */

Documentation

Options

Some options can be passed to htmlToPdfmake function as a second argument.

window

If you use Node, then you'll have to pass the window object (see below).

defaultStyles

You can overwrite the default styles using defaultStyles (see below).

tableAutoSize

By passing tableAutoSize with true, then the program will try to define widths and heights for the tables, based on CSS properties width and height that have been provided to TH or TD.

Example:

var html = htmlToPdfmake(`<table>
  <tr style="height:100px">
    <td style="width:250px">height:100px / width:250px</td>
    <td>height:100px / width:'auto'</td>
  </tr>
  <tr>
    <td style="width:100px">Here it will use 250px for the width because we have to use the largest col's width</td>
    <td style="height:200px">height:200px / width:'auto'</td>
  </tr>
</table>`, {
  tableAutoSize:true
});

// it will return something like:
[ {
    "table": {
      "body": [ [ … ] ],
      "widths": [ 188, "auto" ],
      "heights": [ 75, 151 ]
    }
} ]

HTML tags supported

The below HTML tags are supported:

• DIV / P / SPAN
• BR
• B / STRONG
• I / EM
• S
• UL / OL / LI
• TABLE / THEAD / TBODY / TFOOTER / TR / TH / TD
• H1 to H6
• IMG
• SVG

Default styles

I've defined some default styles for the supported element.

For example, using a <STRONG> will display the word in bold. Or, a link will appear in blue with an underline, and so on...

Here is the list of defaults styles:

{
    b: {bold:true},
    strong: {bold:true},
    u: {decoration:'underline'},
    s: {decoration: 'lineThrough'},
    em: {italics:true},
    i: {italics:true},
    h1: {fontSize:24, bold:true, marginBottom:5},
    h2: {fontSize:22, bold:true, marginBottom:5},
    h3: {fontSize:20, bold:true, marginBottom:5},
    h4: {fontSize:18, bold:true, marginBottom:5},
    h5: {fontSize:16, bold:true, marginBottom:5},
    h6: {fontSize:14, bold:true, marginBottom:5},
    a: {color:'blue', decoration:'underline'},
    strike: {decoration: 'lineThrough'},
    p: {margin:[0, 5, 0, 10]},
    ul: {marginBottom:5},
    li: {marginLeft:5},
    table: {marginBottom:5},
    th: {bold:true, fillColor:'#EEEEEE'}
  }

Please, note that the above default styles are stronger than the ones defined in the style classes. Read below how to overwrite them.

Customize style

Each converted element will have an associated style-class called html-tagname.

For example, if you want all <STRONG> tags to be highlighted with a yellow backgroud you can use html-strong in the styles definition:

var html = htmlToPdfmake(`
  <p>
    This sentence has <strong>a highlighted word</strong>, but not only.
  </p>
  `);

var docDefinition = {
  content: [
    html
  ],
  styles:{
    'html-strong':{
      background:'yellow' // it will add a yellow background to all <STRONG> elements
    }
  }
};

var pdfDocGenerator = pdfMake.createPdf(docDefinition);

CSS class and style

The class and styles for the elements will also be added.

var html = htmlToPdfmake(`
  <p>
    This sentence has <span style="font-weight:bold" class="red">a bold and red word</span>.
  </p>
  `);

/*
It returns:
{
  text: [
    {
      text: 'This sentence has '
    },
    {
      text: 'a bold and red word',
      style: ['red', 'html-span'], // 'red' added because of `class="red"`
      bold: true // added because of `style="font-weight:bold"`
    },
    {
      text: '.'
    }
  ],
  margin: [0, 5, 0, 10],
  style: ['html-p']
}
*/

var docDefinition = {
 content: [
   html
 ],
 styles:{
   red:{ // we define the class called "red"
     color:'red'
   }
 }
};

var pdfDocGenerator = pdfMake.createPdf(docDefinition);

Please, note that the default styles are stronger than the ones defined in the style classes. For example, if you define a class html-a to change all links in purple, then it won't work because the default styles will overwrite it:

var docDefinition = {
 content: [
   html
 ],
 styles:{
   'html-a':{
     color:'purple' // it won't work: all links will remain 'blue'
   }
 }
};

To make it work, you have to either delete the default styles, or change it with a new value. Starting v1.1.0, an option parameter is available as a second parameter.

Example: you want <li> to not have a margin-left, and <a> to be 'purple' and without 'underline' style:

var html = htmlToPdfmake('<ul><li>this is <a href="...">a link</a></li><li>another item</li><li class="with-margin">3rd item with a margin</li></ul>', {
  defaultStyles:{ // change the default styles
    a:{ // for <A>
      color:'purple', // all links should be 'purple'
      decoration:'' // remove underline
    },
    li:'' // remove all default styles for <LI>
  }
});

var docDefinition = {
 content: [
   html
 ],
 styles:{
   'with-margin':{
     marginLeft: 30 // apply a margin with the specific class is used
   }
 }
};

Units

PDFMake uses pt units for the numbers. html-to-pdfmake will check the inline style to see if a number with unit is provided, then it will convert it to pt.

It only works for px, pt and rem (for rem it's based on 1rem = 16px);

Examples:

• font-size:16px will be converted to fontSize:12
• margin:1em will be ignored because it's not a valid unit

<img>

The <img> tag is supported, however the src attribute must already be a base64 encoded content (as describe in the PDFMake documentation).

This is too complex and out of the scope of this module to find and convert the image source to a base64 format. You can check this Stackoverflow question to know the different ways to get a base64 encoded content from an image.

page break

You can use pageBreakBefore and a CSS class that you'll apply to your elements to identify when to add a page break:

var html = htmlToPdfmake(`
  <div>
    <h1>My title on page 1</h1>
    <p>
      This is my paragraph on page 1.
    </p>
    <h1 class="pdf-pagebreak-before">My title on page 2</h1>
    <p>This is my paragraph on page 2.</p>
  </div>
`);

var docDefinition = {
  content: [
    html
  ],
  pageBreakBefore: function(currentNode) {
    return currentNode.style && currentNode.style.indexOf('pdf-pagebreak-before') > -1;
  }
};

var pdfDocGenerator = pdfMake.createPdf(docDefinition);

See example.js to see another example.

Special properties

PDFMake provides some special attributes, like widths or heights for table, or fit for image, and more. To apply these special attributes, you have to use the attribute data-pdfmake on your HTML elements, and then pass the special attributes as a JSON string.

<!-- Example with `widths:[100,"*","auto"]` and `heights:40` to apply to a `table`. -->

<table data-pdfmake="{&quot;widths&quot;:[100,&quot;*&quot;,&quot;auto&quot;],&quot;heights&quot;:40}">
  <tr>
    <td colspan="3">Table with <b>widths=[100,"*","auto"]</b> and <b>heights=40</b></th>
  </tr>
  <tr>
    <td>Cell1</td>
    <td>Cell2</td>
    <td>Cell3</td>
  </tr>
</table>

The expression provided by data-pdfmake must be a valid JSON string because it will be translated with JSON.parse().

<hr>

An <hr> can also be customized using data-pdfmake. Some default styles are applied to this element:

{
  left:0, // the left position
  width:514, // should be OK with a A4 page
  color:'black', // the color of the line
  thickness:0.5, // how thick the line must be
  margin:[0,12,0,12] // same order as PDFMake, meaning: [left, top, right, bottom]
}

See the example.js file to see a <hr> example.

Use with Node

To use it in a Node script you need to install jsdom:

npm install jsdom

Then in your JS file:

var pdfMake = require("pdfmake/build/pdfmake");
var pdfFonts = require("pdfmake/build/vfs_fonts");
pdfMake.vfs = pdfFonts.pdfMake.vfs;
var fs = require('fs');
var jsdom = require("jsdom");
var { JSDOM } = jsdom;
var { window } = new JSDOM("");
var htmlToPdfMake = require("html-to-pdfmake");

var html = htmlToPdfMake(`<div>the html code</div>`, {window:window});

var docDefinition = {
  content: [
    html
  ]
};

var pdfDocGenerator = pdfMake.createPdf(docDefinition);
pdfDocGenerator.getBuffer(function(buffer) {
  fs.writeFileSync('example.pdf', buffer);
});

Examples

You can find more examples in example.js which will create example.pdf:

npm install
node example.js

Donate

You can support my work by making a donation, or by visiting my Github Sponsors page. Thank you!