Here’s a guide to creating a collapsible timeline using CSS3 and Vanilla JavaScript. This type of timeline is excellent for presenting information in a structured and interactive way, allowing users to expand and collapse sections as needed. It enhances user experience by making content easily digestible and accessible.
<meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover"><link rel='stylesheet' href='https://fonts.googleapis.com/css2?family=IBM+Plex+Sans:wght@400;700&display=swap'>
Adding the Necessary Meta and Font Information
To begin, you’ll need to include the viewport meta tag and the IBM Plex Sans font from Google Fonts in the <head> section of your HTML document. This ensures proper rendering across different devices and provides a visually appealing typeface.
Crafting the HTML Structure
Next, set up the basic HTML structure for your collapsible timeline. This includes the main timeline container, individual timeline items, and the necessary elements for the expand/collapse functionality. Each timeline item will consist of a header (containing the date, title, and arrow button) and a body (containing the detailed information). Also including expand and collapse all buttons.
<svg display="none">
<symbol id="arrow">
<polyline points="7 10,12 15,17 10" fill="none" stroke="currentcolor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2" />
</symbol>
</svg>
<h1>A Brief History of Unix Time</h1>
<div id="timeline" class="timeline">
<div class="btn-group">
<button class="btn" type="button" data-action="expand">Expand All</button>
<button class="btn" type="button" data-action="collapse">Collapse All</button>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item1" aria-labelledby="item1-name" aria-expanded="false" aria-controls="item1-ctrld" aria-haspopup="true" data-item="1">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item1-name" class="timeline__meta">
<time class="timeline__date" datetime="1970-01-01">January 1, 1970</time><br>
<strong class="timeline__title">Unix Epoch</strong>
</span>
</div>
<div class="timeline__item-body" id="item1-ctrld" role="region" aria-labelledby="item1" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">This is the day the Unix clock began (or <time datetime="1969-12-31">December 31, 1969</time> if you live behind UTC 😉).</p>
</div>
</div>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item2" aria-labelledby="item2-name" aria-expanded="false" aria-controls="item2-ctrld" aria-haspopup="true" data-item="2">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item2-name" class="timeline__meta">
<time class="timeline__date" datetime="1973-10-17">October 17, 1973</time><br>
<strong class="timeline__title">Digits Within ISO 8601 Format</strong>
</span>
</div>
<div class="timeline__item-body" id="item2-ctrld" role="region" aria-labelledby="item2" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">At 6:36:57 PM UTC, the date in ISO 8601 format (1973-10-17) within the time digits (119731017) appeared for the first time.</p>
</div>
</div>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item3" aria-labelledby="item3-name" aria-expanded="false" aria-controls="item3-ctrld" aria-haspopup="true" data-item="3">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item3-name" class="timeline__meta">
<time class="timeline__date" datetime="2001-09-09">September 9, 2001</time><br>
<strong class="timeline__title">1 Billion Seconds</strong>
</span>
</div>
<div class="timeline__item-body" id="item3-ctrld" role="region" aria-labelledby="item3" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">Unix time reached 1,000,000,000 seconds at 1:46:40 AM UTC. The Danish UNIX User Group celebrated this in Copenhagen, Denmark.</p>
</div>
</div>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item4" aria-labelledby="item4-name" aria-expanded="false" aria-controls="item4-ctrld" aria-haspopup="true" data-item="4">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item4-name" class="timeline__meta">
<time class="timeline__date" datetime="2009-02-13">February 13, 2009</time><br>
<strong class="timeline__title">1,234,567,890 Seconds</strong>
</span>
</div>
<div class="timeline__item-body" id="item4-ctrld" role="region" aria-labelledby="item4" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">At 11:31:30 PM UTC, the digits of the time were 1234567890. This was celebrated worldwide, and even Google had a <a href="https://www.google.com/logos/unix1234567890.gif" target="_blank" rel="noopener">doodle</a> for it.</p>
</div>
</div>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item5" aria-labelledby="item5-name" aria-expanded="false" aria-controls="item5-ctrld" aria-haspopup="true" data-item="5">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item5-name" class="timeline__meta">
<time class="timeline__date" datetime="2033-05-18">May 18, 2033</time><br>
<strong class="timeline__title">2 Billion Seconds</strong>
</span>
</div>
<div class="timeline__item-body" id="item5-ctrld" role="region" aria-labelledby="item5" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">Unix time will reach 2,000,000,000 seconds at 3:33:20 AM UTC.</p>
</div>
</div>
</div>
<div class="timeline__item">
<div class="timeline__item-header">
<button class="timeline__arrow" type="button" id="item6" aria-labelledby="item6-name" aria-expanded="false" aria-controls="item6-ctrld" aria-haspopup="true" data-item="6">
<svg class="timeline__arrow-icon" viewBox="0 0 24 24" width="24px" height="24px">
<use href="#arrow" />
</svg>
</button>
<span class="timeline__dot"></span>
<span id="item6-name" class="timeline__meta">
<time class="timeline__date" datetime="2038-01-19">January 19, 2038</time><br>
<strong class="timeline__title">Unix Epochalypse</strong>
</span>
</div>
<div class="timeline__item-body" id="item6-ctrld" role="region" aria-labelledby="item6" aria-hidden="true">
<div class="timeline__item-body-content">
<p class="timeline__item-p">Also known as the year 2038 problem, clocks running on a 32-bit signed integer will flip from 3:14:08 AM UTC on this day to 8:45:52 PM UTC on December 13, 1901. Therefore, values only from -2,147,483,648 to 2,147,483,647 for the second are supported.</p>
</div>
</div>
</div>
</div>
<script src="./script.js"></script>
Styling the Timeline with CSS
Now it’s time to add some styling to your collapsible timeline. The CSS will handle the layout, appearance, and transitions for the timeline items and their interactive elements. The stylesheet will contain all the styles like the timeline container, timeline items, arrow buttons, and expanded/collapsed states.
* {
border: 0;
box-sizing: border-box;
margin: 0;
padding: 0;
}
:root {
--hue: 223;
--bg: hsl(var(--hue),10%,90%);
--fg: hsl(var(--hue),10%,10%);
--primary: hsl(var(--hue),90%,50%);
--trans-dur: 0.3s;
--trans-timing: cubic-bezier(0.65,0,0.35,1);
font-size: calc(16px + (24 - 16) * (100vw - 320px) / (2560 - 320));
}
a {
color: var(--primary);
transition: color var(--trans-dur);
}
body,
button {
color: var(--fg);
font: 1em/1.5 "IBM Plex Sans", sans-serif;
}
body {
background-color: var(--bg);
height: 100vh;
transition:
background-color var(--trans-dur),
color var(--trans-dur);
}
h1 {
font-size: 2em;
margin: 0 0 3rem;
padding-top: 1.5rem;
text-align: center;
}
.btn {
background-color: var(--fg);
border-radius: 0.25em;
color: var(--bg);
cursor: pointer;
padding: 0.375em 0.75em;
transition:
background-color calc(var(--trans-dur) / 2) linear,
color var(--trans-dur);
-webkit-tap-highlight-color: transparent;
}
.btn:hover {
background-color: hsl(var(--hue),10%,50%);
}
.btn-group {
display: flex;
gap: 0.375em;
margin-bottom: 1.5em;
}
.timeline {
margin: auto;
padding: 0 1.5em;
width: 100%;
max-width: 36em;
}
.timeline__arrow {
background-color: transparent;
border-radius: 0.25em;
cursor: pointer;
flex-shrink: 0;
margin-inline-end: 0.25em;
outline: transparent;
width: 2em;
height: 2em;
transition:
background-color calc(var(--trans-dur) / 2) linear,
color var(--trans-dur);
-webkit-appearance: none;
appearance: none;
-webkit-tap-highlight-color: transparent;
}
.timeline__arrow:focus-visible,
.timeline__arrow:hover {
background-color: hsl(var(--hue),10%,50%,0.4);
}
.timeline__arrow-icon {
display: block;
pointer-events: none;
transform: rotate(-90deg);
transition: transform var(--trans-dur) var(--trans-timing);
width: 100%;
height: auto;
}
.timeline__date {
font-size: 0.833em;
line-height: 2.4;
}
.timeline__dot {
background-color: currentColor;
border-radius: 50%;
display: inline-block;
flex-shrink: 0;
margin: 0.625em 0;
margin-inline-end: 1em;
position: relative;
width: 0.75em;
height: 0.75em;
}
.timeline__item {
position: relative;
padding-bottom: 2.25em;
}
.timeline__item:not(:last-child):before {
background-color: currentColor;
content: "";
display: block;
position: absolute;
top: 1em;
left: 2.625em;
width: 0.125em;
height: 100%;
transform: translateX(-50%);
}
[dir="rtl"] .timeline__arrow-icon {
transform: rotate(90deg);
}
[dir="rtl"] .timeline__item:not(:last-child):before {
right: 2.625em;
left: auto;
transform: translateX(50%);
}
.timeline__item-header {
display: flex;
}
.timeline__item-body {
border-radius: 0.375em;
overflow: hidden;
margin-top: 0.5em;
margin-inline-start: 4em;
height: 0;
}
.timeline__item-body-content {
background-color: hsl(var(--hue),10%,50%,0.2);
opacity: 0;
padding: 0.5em 0.75em;
visibility: hidden;
transition:
opacity var(--trans-dur) var(--trans-timing),
visibility var(--trans-dur) steps(1,end);
}
.timeline__meta {
width: 100%;
}
.timeline__title {
font-size: 1.5em;
line-height: 1.333;
}
/* Expanded state */
.timeline__item-body--expanded {
height: auto;
}
.timeline__item-body--expanded .timeline__item-body-content {
opacity: 1;
visibility: visible;
transition-delay: var(--trans-dur), 0s;
}
.timeline__arrow[aria-expanded="true"] .timeline__arrow-icon {
transform: rotate(0);
}
/* Dark theme */
@media (prefers-color-scheme: dark) {
:root {
--bg: hsl(var(--hue),10%,10%);
--fg: hsl(var(--hue),10%,90%);
--primary: hsl(var(--hue),90%,70%);
}
}
Implementing the Collapsible Functionality with JavaScript
Finally, let’s bring the timeline to life with JavaScript. This code will handle the expanding and collapsing of timeline items when the user clicks on the arrow buttons. This JavaScript will control the expand/collapse all buttons functionality.
window.addEventListener("DOMContentLoaded",() => {
const ctl = new CollapsibleTimeline("#timeline");
});
class CollapsibleTimeline {
constructor(el) {
this.el = document.querySelector(el);
this.init();
}
init() {
this.el?.addEventListener("click",this.itemAction.bind(this));
}
animateItemAction(button,ctrld,contentHeight,shouldCollapse) {
const expandedClass = "timeline__item-body--expanded";
const animOptions = {
duration: 300,
easing: "cubic-bezier(0.65,0,0.35,1)"
};
if (shouldCollapse) {
button.ariaExpanded = "false";
ctrld.ariaHidden = "true";
ctrld.classList.remove(expandedClass);
animOptions.duration *= 2;
this.animation = ctrld.animate([
{ height: `${contentHeight}px` },
{ height: `${contentHeight}px` },
{ height: "0px" }
],animOptions);
} else {
button.ariaExpanded = "true";
ctrld.ariaHidden = "false";
ctrld.classList.add(expandedClass);
this.animation = ctrld.animate([
{ height: "0px" },
{ height: `${contentHeight}px` }
],animOptions);
}
}
itemAction(e) {
const { target } = e;
const action = target?.getAttribute("data-action");
const item = target?.getAttribute("data-item");
if (action) {
const targetExpanded = action === "expand" ? "false" : "true";
const buttons = Array.from(this.el?.querySelectorAll(`[aria-expanded="${targetExpanded}"]`));
const wasExpanded = action === "collapse";
for (let button of buttons) {
const buttonID = button.getAttribute("data-item");
const ctrld = this.el?.querySelector(`#item${buttonID}-ctrld`);
const contentHeight = ctrld.firstElementChild?.offsetHeight;
this.animateItemAction(button,ctrld,contentHeight,wasExpanded);
}
} else if (item) {
const button = this.el?.querySelector(`[data-item="${item}"]`);
const expanded = button?.getAttribute("aria-expanded");
if (!expanded) return;
const wasExpanded = expanded === "true";
const ctrld = this.el?.querySelector(`#item${item}-ctrld`);
const contentHeight = ctrld.firstElementChild?.offsetHeight;
this.animateItemAction(button,ctrld,contentHeight,wasExpanded);
}
}
}
Adding Footer Assets
If any footer assets are required they should be placed here.
With these steps, you have successfully created a collapsible timeline using CSS3 and Vanilla JavaScript.
