How show PDF in vanilla JavaScript in Browser🤯
Tags: javascript, codenewbie, webdev, tutorial
Published: 2021-09-06 18:13:07

Yesterday I wondered how to display a PDF document on a website.

I tried with `iframe` to display the document but it didn't work on mobile devices😔.

After some time of searching, I found a solution using the Mozilla PDF.js library😏.

[Live demo](https://pdf-display-in-plain-js.vercel.app)
[GitHub repo](https://github.com/patik123/pdf_display_in_plain_js)

## Mozilla PDF.js

> A general-purpose, web standards-based platform for parsing and rendering PDFs.

Mozilla's PDF.js project is an open-source project licensed under the Apache 2 license, so it can be used in almost any application.

The library basically only allows us PDF files in the browser.


![Interface if we open the file in browser](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/8vehfh2agmhdng3hp7pg.gif)
 

If you look in detail at the UI of the browser you will find that it is the same as in Mozilla Firefox, if you open the PDF in the browser.

A demo version of the browser is available at [this link](https://mozilla.github.io/pdf.js/web/viewer.html).

However, if you do not need all these features in your application then there is the option of using the PDF.js API.

[More about PDF.js](https://mozilla.github.io/pdf.js/)


## How to build PDF renderer

First, we need to add the PDF.js library to our website, we do it with a simple line.

I am using PDF.js version 2.0.943. In other versions, changes to the API may occur.

```html
<script src="https://cdnjs.cloudflare.com/ajax/libs/pdf.js/2.0.943/pdf.min.js"></script>
```

Our app will consist of navigation keys with which we will be able to go to the next, previous page and enlarge or reduce the document.

```html
<div class="pdf-toolbar">
   <div id="navigation_controls">
      <button class="pdf-toolbar-button" id="previous">Previous</button>
      <input class="pdf-input" id="current_page" value="1" type="number"/>
      <button class="pdf-toolbar-button" id="next">Next</button>
    </div>

   <div id="zoom_controls">  
     <button class="pdf-toolbar-button" id="zoom_in">+</button>
     <button class="pdf-toolbar-button" id="zoom_out">-</button>
    </div>
</div>
```

Our PDF document is displayed in a canvas element, so we need to embed it.

```html
<div id = "canvas_container">
   <canvas id = "pdf_renderer"> </canvas>
</div>
```

Now let's add some JavaScript.

```jsx
var defaultState = {
    pdf: null,
    currentPage: 1,
    zoom: 1
}

// GET OUR PDF FILE
pdfjsLib.getDocument('file.pdf').then((pdf) => {

    defaultState.pdf = pdf;
    render();

});

// RENDER PDF DOCUMENT
function render() {
    defaultState.pdf.getPage(defaultState.currentPage).then((page) => {

        var canvas = document.getElementById("pdf_renderer");
        var ctx = canvas.getContext('2d');

        var viewport = page.getViewport(defaultState.zoom);

        canvas.width = viewport.width;
        canvas.height = viewport.height;

        page.render({
            canvasContext: ctx,
            viewport: viewport
        });
    });
}

// FUNCTION GO TO PREVIOUS SITE
document.getElementById('previous').addEventListener('click', (e) => {
    if (defaultState.pdf == null || defaultState.currentPage == 1)
        return;
    defaultState.currentPage -= 1;
    document.getElementById("current_page").value = defaultState.currentPage;
    render();
});

// FUNCTION GO TO PREVIOUS NEXT
document.getElementById('next').addEventListener('click', (e) => {
    if (defaultState.pdf == null || defaultState.currentPage > defaultState.pdf._pdfInfo.numPages)
        return;
    defaultState.currentPage += 1;
    document.getElementById("current_page").value = defaultState.currentPage;
    render();
});

// FUNCTION GO TO CUSTUM SITE
document.getElementById('current_page').addEventListener('keypress', (e) => {
    if (defaultState.pdf == null) return;

    var code = (e.keyCode ? e.keyCode : e.which);

    if (code == 13) { // ON CLICK ENTER GO TO SITE TYPED IN TEXT-BOX
        var desiredPage =
            document.getElementById('current_page').valueAsNumber;

        if (desiredPage >= 1 && desiredPage <= defaultState.pdf._pdfInfo.numPages) {
            defaultState.currentPage = desiredPage;
            document.getElementById("current_page").value = desiredPage;
            render();
        }
    }
});

// FUNCTION FOR ZOOM IN
document.getElementById('zoom_in').addEventListener('click', (e) => {
    if (defaultState.pdf == null) return;
    defaultState.zoom += 0.5;
    render();
});

// FUNCTION FOR ZOOM OUT
document.getElementById('zoom_out').addEventListener('click', (e) => {
    if (defaultState.pdf == null) return;
    defaultState.zoom -= 0.5;
    render();
});
```

We have now created a page where we can display any PDF on any device, without downloading.

Here is the look of the final version.

![Final version of app](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/slxim6750ymfa82m4ljm.gif)
 

If you have a CV in PDF on your portfolio, you can now view it in your browser.

I hope this guide helped you, for even more content you can follow me on my [Twitter profile](https://twitter.com/Patik123_).