Tag: Percentage

How I Put the Scroll Percentage in the Browser Title Bar

Some nice trickery from Knut Melvær.

Ultimately the trick boils down to figuring out how far you’ve scrolled on the page and changing the title to show it, like:

document.title = `$  {percent}% $  {post.title}`

Knut’s trick assumes React and installing an additional library. I’m sure that library does all kinds of smart stuff, but if you’re looking to do this “vanilla” style, I’d probably rock something like this…

const percentLabel = document.querySelector("#percent"); const originalTitle = document.title;  window.addEventListener("scroll", () => {   let scrollTop = window.scrollY;   let docHeight = document.body.offsetHeight;   let winHeight = window.innerHeight;   let scrollPercent = scrollTop / (docHeight - winHeight);   let scrollPercentRounded = Math.round(scrollPercent * 100);   percentLabel.innerHTML = scrollPercentRounded;   document.title = `($  {scrollPercentRounded}%) $  {originalTitle}`; });

Here’s a project, and here’s the deployed site so you can see it in action.

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Oh Hey, Padding Percentage is Based on the Parent Element’s Width

I learned something about percentage-based (%) padding today that I had totally wrong in my head! I always thought that percentage padding was based on the element itself. So if an element is 1,000 pixels wide with padding-top: 50%, that padding is 500 pixels. It’s weird having top padding based on width, but that’s how it works — but only sorta. The 50% is based on the parent element’s width, not itself. That’s the part that confused me.

The only time I’ve ever messed with percentage padding is to do the aspect ratio boxes trick. The element is of fluid width, but you want to maintain an aspect ratio, hence the percentage padding trick. In that scenario, the width of the element is the width of the parent, so my incorrect mental model just never mattered.

It doesn’t take much to prove it:

See the Pen
% padding is based on parent, not itself
by Chris Coyier (@chriscoyier)
on CodePen.

Thanks to Cameron Clark for the email about this:

The difference is moot when you have a block element that expands to fill the width of its parent completely, as in every example used in this article. But when you set any width on the element other than 100%, this misunderstanding will lead to baffling results.

They pointed to this article by Aayush Arora who claims that only 1% of developers knew this.

The post Oh Hey, Padding Percentage is Based on the Parent Element’s Width appeared first on CSS-Tricks.

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