<main>
<section></section>
</main>
<aside>
<div class="control">
<input id="size" type="checkbox" />
<label for="size">contain: size</label>
</div>
<div class="control">
<button id="start">start</button>
<button id="reset">reset</button>
<button id="resize">resize container</button>
</div>
</aside>
@import url("https://fonts.googleapis.com/css2?family=Exo:wght@600&display=swap");
html {
width: 100vw;
min-height: 100vh;
}
body {
align-items: center;
background-color: #1d1e22;
color: white;
display: flex;
flex-direction: column;
width: 100vw;
min-height: 100vh;
justify-content: center;
margin: 0;
padding: 0;
font-family: "Exo", Arial, sans-serif;
font-size: 20px;
font-weight: 600;
}
aside {
display: flex;
flex-direction: column;
align-items: center;
padding-top: 20px;
}
button {
margin-top: 40px;
border-radius: 6px;
background-color: transparent;
border: 4px solid #fff;
padding: 10px 20px;
outline: none;
color: #fff;
cursor: pointer;
font-family: "Exo", Arial, sans-serif;
font-size: 20px;
font-weight: 600;
}
button:active {
color: #fff;
border-color: #cfcfcf;
transform: rotate(0.1deg) scale(0.9);
transform-origin: 50% 100%;
}
main {
background-color: #333;
border: 3px solid rebeccapurple;
}
section {
border: 2px solid red;
height: 100px;
margin: 10px;
width: 100px;
}
main.size {
contain: size;
height: 200px;
width: 200px;
}
main.resize {
height: 200px;
width: 300px;
}
View Compiled
const start = document.querySelector('#start');
const reset = document.querySelector('#reset');
const size = document.querySelector('#size');
const resize = document.querySelector('#resize');
const main = document.querySelector('main');
const section = document.querySelector('section');
let timeout;
let resizeObserver;
start.addEventListener('click', function () {
resizeObserver = new ResizeObserver(entries => {
timeout = window.setTimeout(function () {
section.style.width = `${entries[0].contentRect.width + 5}px`;
if (entries[0].contentRect.width > 300) {
resizeObserver.unobserve(main);
window.clearTimeout(timeout);
}
}, 500);
});
resizeObserver.observe(main);
});
reset.addEventListener('click', function () {
section.style.width = '100px';
resizeObserver.unobserve(main);
window.clearTimeout(timeout);
});
size.addEventListener('change', function () {
main.classList.toggle('size', size.checked);
});
resize.addEventListener('click', function () {
main.classList.toggle('resize');
});
This Pen doesn't use any external CSS resources.
This Pen doesn't use any external JavaScript resources.