Syntax Highlighting and Copy Function in Hugo

Notes for Future Use

geeky stuff
#pygments | #highlightjs | #prismjs | #clipboardjs | #jquery | #hugo | #python | #javascript

  • I decided to drop the below functions. I just use whatever applicable/available with Hugo Built-in Functions and Clipboard.js.
  • Please refer to the JS section below.

I tried several methods available as described in Hugo documentation for [Syntax Highlighting] function on my blog. My first attempt was the pre-processed server side approach using [1] Pygments, an external Python-based program. I installed Pygments through pip install, not realizing that Arch has it provided under its package manager called [2] pygmentize.

Probably because I did not really understand how it works and was influenced by the disclaimer in the documentation which says, “Pygments is relatively slow and causes a performance hit when building your site," I dumped the program and tried switching to the client-side approach using JavaScript libraries instead. In addition, since I use ranger which is based on python as my file manager, it takes a few seconds for files to be previewed because it needs to display the syntax coloring as appeared in the image below. Without pygmentize installed, it straight away previews them on the rightmost column but all in a plain white color.

So I turned to [3] Prism.js. It supports 121 languages and line numbers are made available through a plugin too. However, I noticed that a few line numbers from the bottom were missing in every file containing codes. The numbers missing were random so I guessed it depends on the length of the codes written. I was quite disturbed by it so I looked for many ways that perhaps could fix it but the problem still persisted. Thus, I decided to try out Highlight.js.

[4] Highlight.js is super easy to set up. Just follow the installation instruction as described either in its [official website] or in [Hugo documentation] and voilà, it just works. In fact, I needed not to do any extra tweaking because the [Blackburn] theme I am using for my blog has already included it as its main syntax highlighter. This js library by far has the largest number of languages supported and even though it does not support line numbers, I was happy enough with it until I realized that I have this nvim configuration file with long lines queuing and when I viewed it from my mobile phone, scrolled down to the bottom and scrolled back up to the top, it caused the screen to freeze.

That issue resulted in me moving back to Prism.js. I tested out whether or not the same problem as to what I was facing while running the highlight.js would occur by viewing the same file in the browser from my mobile phone. The result was good! Scrolling up and down actions did not at all lead to a frozen screen.


I think that it would be fun if we could copy a text to clipboard with a button which allows this specific function and at the same time, it displays a tooltip following the click on the button however, I quite struggled with this one. This is because I did plenty of trial and error to make it work. When I googled "clipboard button on hugo", the results returned the following first three URLs:-
  1. ngclipboard - Angularjs directive for clipboard.js: I ignored this one as it is based on clipboard.js & is only applicable to an app which I neither have an idea what it is for nor what it is all about ;
  2. clipboard.js — Copy to clipboard without Flash ; &
  3. How to copy TEXT to Clipboard on Button-Click - CodePen
    1. CodePen Approach
      I tested out the approach from the [3rd URL] first. What I did was I copied the codes from the JS section and pasted it to a, let's say copy.js file and saved it in /static/js directory.

      I skipped the CSS part and copied the following codes to the header template (header.html) located in /layouts/partials directory:

      <link href='' rel='stylesheet' type='text/css'> 
      <script src=""></script>
      <script src="/js/copy.js"></script>

      I then created a file containing perl codes (let’s save it as and assigned a copy button as well as a ‘clip’ id attribute to the <pre> tag:

      <button onclick="copyToClipboard('#clip')">Copy to Clipboard</button>
      <pre id="clip" class="line-numbers"><code class="language-perl"># Prints the message using two different delimeters.
      print "Hello, world!\n";
      print qq=Did you say "Hello?"\n=;
      The image below shows how it looked like when being viewed in the browser:

      Notice the “copyToClipboard('#clip')" assigned to the button onclick and the <pre id=“clip”> placed in the file. It simply means that a bookmark (served as a target area) with the ‘clip’ id attribute is created for the <pre> tag and so the button will then function to copy all the codes placed after by the same bookmark.

      Here comes the ugly outcome of clicking the Copy to Clipboard button and having the copied contents pasted into an empty file using my nvim editor:-

      # Prints the message using two different delimeters.print "Hello, world!\n";print qq=Did you say "Hello?"\n=;Copy

      It did not preserve the original layout of the written codes where they got pasted in a continuous mode. Imagine there are 100 lines of codes to be copied, it will take a lot of work to correct the spaces.

    2. Clipboard.js Approach
      Then, I tried out the clipboard.js library as described in the [2nd URL]. I downloaded the zip file and included the extracted script as well as had it instantiated by putting the following lines into the header template, substituting the initial included scripts provided by CodePen above:-

      <!-- clipboard-button-->
      <script src="/js/clipboard.min.js"></script>
      new Clipboard('.btn');

      Using the same file, I replaced the button onclick line with this,

      <button class="btn" data-clipboard-target="#clip">Copy to Clipboard</button>
      I opened the file in the browser, clicked the button, pasted the copied codes in an empty file, and yeay, it worked! The line layout was preserved as it should be.

Now, even though it worked well, I would like to be able to tell whether or not the copying job succeeds before pasting the copied contents to other destination, like there is a tooltip that displays "Copied!" when the button is clicked. For this, I found out that I would need jquery and bootstrap.

I downloaded the zip file of [5] jquery & [6] bootstrap and extracted them to the same /static/js directory. Thanks to this discussion, I was able to get it done successfully by having these lines placed into a separate *.html file (let’s create it as a partial template by the name of copy.html and park it in the /layouts/partials directory).

<link href="/css/bootstrap.min.css" type="text/css" rel="stylesheet"/>
<script src="/js/jquery.min.js"></script>
<script src="/js/clipboard.min.js"></script>
<script src="/js/bootstrap.min.js"></script>

// Tooltip


  trigger: 'click',

function setTooltip(message) {
    .attr('data-original-title', message)

function hideTooltip() {
  setTimeout(function() {
  }, 2000);

// Clipboard

var clipboard = new Clipboard('.btn');

clipboard.on('success', function(e) {

clipboard.on('error', function(e) {

After that, I used the [7] partial call to include the above copy.html template in the header template by adding the following line into it:

{{ partial "copy.html" . }}

Then, I went back to the file to have these lines filled in as replacement to the previous copy button created:

<button class="btn btn-default" data-clipboard-target="#clip" data-placement="bottom" data-toggle="tooltip" title="Copy to Clipboard" button type="button">
  <img src="/img/clippy.svg" width="15">

Whenever I hover over the copy button (in the form of icon| [8] scroll down to the bottom for a demo), there is a tooltip displaying “Copy to Clipboard” and when I clicked the button, it pops up “Copied!” for a successful copying job.

I made my final decision where I chose to use Pygments for Syntax Highlighting. It supports over 300 languages, can display line numbers without any issues and the scrolling actions when viewing files containing a bunch of coding lines from a mobile device appear to be smooth too.

The difference is in order for the copy to clipboard function to work, changes have to be made to the way we assign a bookmark to the <pre> tag, because syntax highlighting works by a different approach where it uses the in-built shortcode called highlight.

So, as opposed to the client-side JavaScript libraries where a bookmark is added to the <pre> tag, we will now have it applied to the <div> tag like the following example:

<script src="/js/jquery.min.js"></script>
<script src="/js/clipboard.min.js"></script>


// Clipboard

new ClipboardJS('.main');

var copyCode = new ClipboardJS('.main', {
target: function(trigger) {
return trigger.previousElementSibling;

copyCode.on('success', function(event) {
    event.trigger.textContent = 'COPIED!';
    window.setTimeout(function() {
        event.trigger.textContent = 'COPY';
    }, 1000);

copyCode.on('error', function(event) { 
    event.trigger.textContent = 'Press "Ctrl + C" to copy';
    window.setTimeout(function() {
        event.trigger.textContent = 'COPY';
    }, 1000);

<button class="main" data-clipboard-target="#clip">

<div id="clip">
# Prints the message using two different delimeters.
print "Hello, world!\n";
print qq=Did you say "Hello?"\n=;
button.main {
    opacity: 0.8;
    font-size: 0.7em;
    background: #000;
    color: #fff;
    border: 2px solid grey;
    padding: 2px 2px 0px 3px; 
    border-radius: 5px;
    float: right;
    overflow: hidden;
The message trigger function only works if a space is placed with <br> tag before the copy button.

Let's see it in action by clicking the copy button below *(I have the button floated on the right with CSS)*. Note though that with Pygments in use, the copy to clipboard function lets the line numbers copied as well, which is something we do not want. Thus, it has its cons however, should we need the line numbers displayed, it at least shows the complete line numbers.
1# Prints the message using two different delimeters.
2print "Hello, world!\n";
3print qq=Did you say "Hello?"\n=;

Kali terakhir halaman ini dikemaskini/disemak semula adalah pada .