Author: Phil

Phil Reynolds

September 20, 2021

Simple Javascript Hideable Sections

Bootstrap has a very helpful "collapse" class. However, where possible I'm trying to avoid using large frameworks for the sake of line or two of code.

There's no need to load in an entire library or framework if you are only looking to use one or two features. It's lazy programming to do this. Often it can facilitate an increase of pace if you're looking to develop something quickly, but in these cases I will always strongly advocate for a reduction in scope rather than bolting on additional libraries and frameworks which have potential to impact user experience or introduce vulnerabilities further down the road.

In an upcoming post (now released here), I was looking to add a small section which was not important to the overall message of the article, but I wanted visitors to be able to read it should they want. Look for the "How we build a Prototype" post when it goes live to see that use case.

I've used the Bootstrap collapse functionality extensively in the past, however this has always been when I've been leveraging the full toolkit or at least a lot of other helpers from it.

For our developer blog, one of the key aims is to keep it as lightweight as possible. We use Jekyll as an SSGand have as little JS running as possible. We have Bootstrap on the main developer page for buttons and cards, but it's in the backlog to strip this out and go back to basics.

To solve this problem with Vanilla JS and no Bootstrap, the first port of call, as with all problems like this, was a quick Google. The first result was from W3Schools. I'm always skeptical of W3Schools, and this page is a great example of why. The code is outdated and way overcomplicated. There were also some stackoverflow results, but most were outdated or relying heavily on jQuery. (If you're unsure why this is a problem, have a look here, ES6 is great.)

No luck there, time to build it from scratch. What do I want it to do? I want a button to unhide a section, then hide it when pressed again.

First the button

<a onclick="collapseElement('#note')">Title of what to reveal <i class="fas fa-chevron-down"></i></a>
<p id="note" class="hideable">Revealable text content</p>

Then toggle the class with some js

function collapseElement(input) {
    const section = document.querySelector(input);

Then set it to reveal with a transition

.collapse {
  max-height: 0;
  overflow: hidden;
  transition: all .5s cubic-bezier(0, 1, 0, 1);
    max-height: 20rem;
    transition: all .5s ease-in-out;

The output here I think is way simpler than anything I could find online. There's no need to overcomplicate it. One thing that could be done better is to swap the down chevron to an up chevron, I might add that later on.

Here it is in action.

Click to reveal the section

This is the hidden section. With some content. Together, we have the power to revolutionise the industry. Innovative technologies, such as artificial intelligence and blockchain, are ready to transform access to justice, legal decision-making and legal advice. The Legal Innovation Lab Wales is here to accelerate advancements in the industry and invigorate growth in Legal Tech in Wales and beyond.

Thanks for reading, if you have any feedback or suggestions please get in touch!