HTML preprocessors can make writing HTML more powerful or convenient. For instance, Markdown is designed to be easier to write and read for text documents and you could write a loop in Pug.
In CodePen, whatever you write in the HTML editor is what goes within the <body>
tags in a basic HTML5 template. So you don't have access to higher-up elements like the <html>
tag. If you want to add classes there that can affect the whole document, this is the place to do it.
In CodePen, whatever you write in the HTML editor is what goes within the <body>
tags in a basic HTML5 template. If you need things in the <head>
of the document, put that code here.
The resource you are linking to is using the 'http' protocol, which may not work when the browser is using https.
CSS preprocessors help make authoring CSS easier. All of them offer things like variables and mixins to provide convenient abstractions.
It's a common practice to apply CSS to a page that styles elements such that they are consistent across all browsers. We offer two of the most popular choices: normalize.css and a reset. Or, choose Neither and nothing will be applied.
To get the best cross-browser support, it is a common practice to apply vendor prefixes to CSS properties and values that require them to work. For instance -webkit-
or -moz-
.
We offer two popular choices: Autoprefixer (which processes your CSS server-side) and -prefix-free (which applies prefixes via a script, client-side).
Any URLs added here will be added as <link>
s in order, and before the CSS in the editor. You can use the CSS from another Pen by using its URL and the proper URL extension.
You can apply CSS to your Pen from any stylesheet on the web. Just put a URL to it here and we'll apply it, in the order you have them, before the CSS in the Pen itself.
You can also link to another Pen here (use the .css
URL Extension) and we'll pull the CSS from that Pen and include it. If it's using a matching preprocessor, use the appropriate URL Extension and we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.
JavaScript preprocessors can help make authoring JavaScript easier and more convenient.
Babel includes JSX processing.
Any URL's added here will be added as <script>
s in order, and run before the JavaScript in the editor. You can use the URL of any other Pen and it will include the JavaScript from that Pen.
You can apply a script from anywhere on the web to your Pen. Just put a URL to it here and we'll add it, in the order you have them, before the JavaScript in the Pen itself.
If the script you link to has the file extension of a preprocessor, we'll attempt to process it before applying.
You can also link to another Pen here, and we'll pull the JavaScript from that Pen and include it. If it's using a matching preprocessor, we'll combine the code before preprocessing, so you can use the linked Pen as a true dependency.
Search for and use JavaScript packages from npm here. By selecting a package, an import
statement will be added to the top of the JavaScript editor for this package.
Using packages here is powered by esm.sh, which makes packages from npm not only available on a CDN, but prepares them for native JavaScript ESM usage.
All packages are different, so refer to their docs for how they work.
If you're using React / ReactDOM, make sure to turn on Babel for the JSX processing.
If active, Pens will autosave every 30 seconds after being saved once.
If enabled, the preview panel updates automatically as you code. If disabled, use the "Run" button to update.
If enabled, your code will be formatted when you actively save your Pen. Note: your code becomes un-folded during formatting.
Visit your global Editor Settings.
<link rel="preconnect" href="https://fonts.gstatic.com">
<link href="https://fonts.googleapis.com/css2?family=Josefin+Sans&display=swap" rel="stylesheet">
<h1>Corona Simulator</h1>
<main>
<section class="legend">
<div class="legend-color healthy"></div>
<div id="legend-healthy"> Healthy</div>
<div class="legend-color infected"></div>
<div id="legend-infected">Infected</div>
<div class="legend-color immune"></div>
<div id="legend-immune">Immune</div>
<div class="legend-color dead"></div>
<div id="legend-dead">Dead</div>
</section>
<section class="buttons">
<button type="button" class="button" onclick="reset()">Reset</button>
<label class="switch">
<input type="checkbox" name="use-js" id="use-js" onchange="reloadLang()">
<span class="slider button">
<div id="active-lang">Rust</div>
</span>
</label>
<button type="button" class="next button" onclick="advance()">Next Day</button>
<button id="start-stop-button" type="button" class="start button" onclick="startStop()">Start Simulation</button>
</section>
<section>
<form id="settings" class="config-form">
<label for="width">Width:</label>
<input type="number" name="width" value="20" min="0" title="Number of cells in row" onchange="reloadSettings()">
<label for="height">Height:</label>
<input type="number" name="height" value="5" min="0" title="Number of cells in column" onchange="reloadSettings()">
<label for="radius">Radius:</label>
<input type="number" name="radius" value="2" min="0" title="How many cells the virus can spread in a single day" onchange="reloadSettings()">
<label for="infection_rate">Infection Rate:</label>
<input type="number" name="infection_rate" value="0.02" step="0.0001" min="0.0" max="1.0" title="Chance that a person is infected by a single infected patient in the infection radius." onchange="reloadSettings()">
<label for="death_rate">Death Rate:</label>
<input type="number" name="death_rate" value="0.03" step="0.01" min="0.0" max="1.0" title="Chance that an infected person dies in a day." onchange="reloadSettings()">
<label for="recovery">Days until recovered:</label>
<input type="number" name="recovery" value="10" min="1" max="20" title="Chance that an infected person dies in a day." onchange="reloadSettings()">
<label for="delay">Simulation delay:</label>
<input type="number" name="delay" value="300" min="1" title="Delay between simulation steps in ms.">
</form>
</section>
<!-- Dynamic JS will be inserted here -->
</main>
<footer>
2020 - WASM Demo App by Jakob Meier - <a target="_blank" href="https://github.com/jakmeier/covid-sim">Source Code</a>
</footer>
body {
text-align: center;
background-color: #e1aa7d;
font-family: "Josefin Sans", Arial, Helvetica, sans-serif;
}
main {
display: grid;
grid-template-columns: 1fr 1fr 1fr;
grid-template-areas: "legend buttons form" "humans humans humans";
width: 100%;
}
.config-form {
grid-area: form;
display: grid;
grid-template-columns: min-content minmax(max-content, 200px);
align-items: center;
justify-content: center;
grid-gap: 10px;
margin: 20px;
}
.buttons {
grid-area: buttons;
display: grid;
grid-template-areas: "reset slider" "next next" "start start";
grid-template-rows: 90px auto;
grid-template-columns: 1fr 1fr;
justify-content: center;
justify-items: center;
grid-gap: 0 10px;
height: 100%;
align-content: space-around;
}
.next {
grid-area: next;
}
.start {
grid-area: start;
}
.buttons button {
margin: 10px;
font-size: xx-large;
width: 100%;
height: 70px;
}
.button {
border-radius: 1em;
background-color: #b6d094;
border-style: solid;
border-color: #2e2836;
border-width: 2px;
color: black;
}
#active-lang {
margin: 20px;
}
input {
background-color: #b6d094;
border-color: #2e2836;
}
.legend {
grid-area: legend;
display: grid;
justify-content: center;
grid-template-columns: min-content min-content;
justify-items: start;
align-items: center;
}
.legend-color {
width: 3em;
height: 3em;
margin: 0.5em;
}
.container {
margin-top: 20px;
grid-area: humans;
display: grid;
grid-gap: 1px;
}
.human {
width: 100%;
padding-top: 100%;
}
.healthy {
background-color: #be8a60;
}
.infected {
background-color: #6a2e35;
}
.immune {
background-color: #b6d094;
}
.dead {
background-color: #2e2836;
}
/* Slider, adapted from https://www.w3schools.com/howto/howto_css_switch.asp */
/* The switch - the box around the slider */
.switch {
position: relative;
display: inline-block;
width: 100%;
height: 100%;
font-size: xx-large;
}
/* Hide default HTML checkbox */
.switch input {
opacity: 0;
width: 0;
height: 0;
}
/* The slider */
.slider {
position: absolute;
top: 10px;
left: 0;
right: 0;
bottom: 10px;
-webkit-transition: 0.4s;
transition: 0.4s;
}
.slider:before {
position: absolute;
content: "";
height: 50px;
width: 50px;
left: 10px;
bottom: 10px;
background-color: white;
-webkit-transition: 0.4s;
transition: 0.4s;
border-radius: 50%;
}
input:checked + .slider {
background-color: #be8a60;
}
input:checked + .slider:before {
left: calc(100% - 60px);
}
footer {
margin-top: 50px;
height: 200px;
}
@media (max-width: 1200px) {
main {
grid-template-columns: 1fr 1fr;
grid-template-areas: "form legend" "buttons buttons" "humans humans";
}
}
@media (max-width: 800px) {
main {
grid-template-columns: 1fr;
grid-template-areas: "form" "legend" "buttons" "humans";
}
.legend {
grid-template-columns: min-content max-content min-content max-content;
}
}
// Note: The code pen code is slightly adapted compared to the source code show in my repository at https://github.com/jakmeier/covid-sim/.
// The reason is that here we are not using a bundler (WebPack).
// For the CodePen, I used `wasm-pack publish` to publish a package to npm.
// 1) wasm-pack build --scope jakmeier --target web
// 2) wasm-pack pack
// 3) wasm-pack publish --access public
//
// Here, we are loading this package through a public CDN. (Thanks unpkg!)
// The default export of the package gives access to a init() function that will load the WASM module.
import init, { Simulation } from "https://unpkg.com/@jakmeier/wasm-covid-sim@1.0.0/wasm_covid_sim.js";
// Note that the CDN that Skypack CDB, which CodePen uses by default, does not work. It does not export the wasm file at the time I was testing it.
// FAILS:
// import init, {Simulation} from 'https://cdn.skypack.dev/@jakmeier/wasm-covid-sim@1.0.0';
const HEALTHY = 0;
const INFECTED_DAY_0 = 1;
const INFECTED_DAY_MAX = 64;
const IMMUNE = 100;
const DEAD = 101;
let humans;
let htmlNodes;
let container;
let simulation;
let jsSimulation;
let rustSimulation;
let useJs = false;
let healthy = 0;
let infected = 0;
let immune = 0;
let dead = 0;
init()
.then(() => {
if (document.readyState != "loading") {
main();
} else {
document.addEventListener("DOMContentLoaded", main);
}
})
.catch((e) => console.log("failed loading wasm", e));
function main() {
const mainElement = document.getElementsByTagName("main")[0];
container = document.createElement("div");
container.classList.add("container");
mainElement.appendChild(container);
rustSimulation = new Simulation();
jsSimulation = new JsSimulation();
simulation = rustSimulation;
humans = new Uint8Array();
reloadSettings();
updateView();
// Advance on space bar
document.addEventListener("keydown", (evt) => {
if (evt.key === " ") {
advance();
}
});
// Make functions globally available for onclick handler on button
window.advance = advance;
window.startStop = startStop;
window.reloadSettings = reloadSettings;
window.reloadLang = reloadLang;
window.reset = reset;
}
function reloadSettings() {
const form = document.getElementById("settings");
const data = new FormData(form);
const w = parseInt(data.get("width"));
const h = parseInt(data.get("height"));
const radius = parseInt(data.get("radius"));
const recoveryDays = parseInt(data.get("recovery"));
const infectionRate = parseFloat(data.get("infection_rate"));
const deathRate = parseFloat(data.get("death_rate"));
if (w * h != humans.length) {
// Replace current state, set all values to 0 (HEALTHY)
humans = new Uint8Array(w * h);
generateHtmlNodes(w, h);
}
jsSimulation.reconfigure(
w,
h,
radius,
recoveryDays,
infectionRate,
deathRate
);
rustSimulation.reconfigure(
w,
h,
radius,
recoveryDays,
infectionRate,
deathRate
);
}
function reloadLang() {
useJs = document.getElementById("use-js").checked;
if (useJs) {
simulation = jsSimulation;
document.getElementById("active-lang").textContent = "JS";
} else {
simulation = rustSimulation;
document.getElementById("active-lang").textContent = "Rust";
}
}
function reset() {
humans = new Uint8Array(humans.length);
htmlNodes.forEach((node) => {
node.classList.add("healthy");
node.classList.remove("infected");
node.classList.remove("dead");
node.classList.remove("immune");
});
// Infect patient 0
setState(Math.floor(humans.length / 2), INFECTED_DAY_0);
updateView();
}
function advance() {
let newState = new Uint8Array(humans.length);
const t0 = performance.now();
simulation.next_day(humans, newState);
const t1 = performance.now();
for (let i = 0; i < htmlNodes.length; i++) {
if (newState[i] != humans[i]) {
setState(i, newState[i]);
}
}
updateView();
humans = newState;
const t2 = performance.now();
if (useJs) {
console.log(`Updated in ${t2 - t0}ms (${t1 - t0}ms computing in JS, ${t2 - t1}ms DOM updates in JS)`);
} else {
console.log(`Updated in ${t2 - t0}ms (${t1 - t0}ms computing in Rust, ${t2 - t1}ms DOM updates in JS)`);
}
}
let handle;
let isRunning = false;
function startStop() {
const form = document.getElementById("settings");
let simulationDelay = form.elements["delay"].value;
if (isRunning) {
clearInterval(handle);
document.getElementById("start-stop-button").innerText = "Start Simulation";
} else {
handle = setInterval(advance, simulationDelay);
document.getElementById("start-stop-button").innerText = "Stop Simulation";
}
isRunning = !isRunning;
}
function generateHtmlNodes(w, h) {
const t0 = performance.now();
while (container.firstChild) {
container.removeChild(container.lastChild);
}
container.style.gridTemplateColumns = `repeat(${w},1fr)`;
htmlNodes = [];
for (let y = 0; y < h; y++) {
for (let x = 0; x < w; x++) {
const cell = document.createElement("div");
cell.classList.add("human");
cell.classList.add("healthy");
cell.addEventListener("click", () => toggleInfected(x + y * w));
container.appendChild(cell);
htmlNodes.push(cell);
}
}
const t1 = performance.now();
console.log(`Created HTML nodes in ${t1 - t0}ms`);
healthy = w * h;
infected = 0;
immune = 0;
dead = 0;
// Infect patient 0
setState(Math.floor(humans.length / 2), INFECTED_DAY_0);
}
function updateView() {
document.getElementById("legend-healthy").innerText = `Healthy (${healthy})`;
document.getElementById(
"legend-infected"
).innerText = `Infected (${infected})`;
document.getElementById("legend-immune").innerText = `Immune (${immune})`;
document.getElementById("legend-dead").innerText = `Dead (${dead})`;
}
function setState(i, state) {
// Remove old class
if (humans[i] == HEALTHY) {
htmlNodes[i].classList.remove("healthy");
healthy -= 1;
} else if (humans[i] >= INFECTED_DAY_0 && humans[i] <= INFECTED_DAY_MAX) {
htmlNodes[i].classList.remove("infected");
infected -= 1;
} else if (humans[i] == IMMUNE) {
htmlNodes[i].classList.remove("immune");
immune -= 1;
} else if (humans[i] == DEAD) {
htmlNodes[i].classList.remove("dead");
dead -= 1;
}
// Add new class
if (state == HEALTHY) {
htmlNodes[i].classList.add("healthy");
healthy += 1;
} else if (state >= INFECTED_DAY_0 && state <= INFECTED_DAY_MAX) {
htmlNodes[i].classList.add("infected");
infected += 1;
} else if (state == IMMUNE) {
htmlNodes[i].classList.add("immune");
immune += 1;
} else if (state == DEAD) {
htmlNodes[i].classList.add("dead");
dead += 1;
}
humans[i] = state;
}
function toggleInfected(index) {
if (humans[index] == HEALTHY) {
setState(index, INFECTED_DAY_0);
} else {
setState(index, HEALTHY);
}
updateView();
}
/***************
* lib.js
***************/
// Mirroring the behaviour of lib.rs in JavaScript for measuring the performance difference.
class JsSimulation {
constructor(name, year) {
this.w = 0;
this.h = 0;
this.recovery = 0;
this.infection_rate = 0.0;
this.death_rate = 0.0;
}
reconfigure(w, h, radius, recovery, infection_rate, death_rate) {
this.w = w;
this.h = h;
this.radius = radius;
this.recovery = recovery;
this.infection_rate = infection_rate;
this.death_rate = death_rate;
}
next_day(input, output) {
for (let x = 0; x < this.w; x++) {
for (let y = 0; y < this.h; y++) {
const current = this.get(input, x, y);
let next = current;
if (current == HEALTHY) {
if (this.chance_to_catch_covid_today(input, x, y) > Math.random()) {
next = INFECTED_DAY_0 + 1;
}
} else if (current >= INFECTED_DAY_0 && current <= INFECTED_DAY_MAX) {
if (this.death_rate > Math.random()) {
next = DEAD;
} else if (
current >= INFECTED_DAY_0 &&
current <= INFECTED_DAY_MAX &&
current - INFECTED_DAY_0 >= this.recovery
) {
next = IMMUNE;
} else {
next = current + 1;
}
}
this.set(output, x, y, next);
}
}
}
chance_to_catch_covid_today(input, x, y) {
let infected_neighbours = 0;
const start_x = Math.max(0, x - this.radius);
const start_y = Math.max(0, y - this.radius);
const end_x = Math.min(x + this.radius + 1, this.w);
const end_y = Math.min(y + this.radius + 1, this.h);
for (let j = start_y; j < end_y; j++) {
for (let i = start_x; i < end_x; i++) {
const neighbour = this.get(input, i, j);
if (neighbour >= INFECTED_DAY_0 && neighbour <= INFECTED_DAY_MAX) {
infected_neighbours += 1;
}
}
}
let p_healthy = Math.pow(1.0 - this.infection_rate, infected_neighbours);
return 1.0 - p_healthy;
}
get(input, x, y) {
return input[x + y * this.w];
}
set(output, x, y, status) {
output[x + y * this.w] = status;
}
}
Also see: Tab Triggers