custom properties

Updating a CSS Variable with JavaScript

Here's a CSS variable (formally called a "CSS custom property"):

:root {
  --mouse-x: 0px;
  --mouse-y: 0px;
}

Perhaps you use them to set a position:

.mover {
  left: var(--mouse-x);
  top: var(--mouse-y);
}

To update those values from JavaScript, you'd:

let root = document.documentElement;

root.addEventListener("mousemove", e => {
  root.style.setProperty('--mouse-x', e.clientX + "px");
  root.style.setProperty('--mouse-y', e.clientY + "px");
});

That's all.

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Super-Powered Grid Components with CSS Custom Properties

A little while ago, I wrote a well-received article about combining CSS variables with CSS grid to help build more maintainable layouts. But CSS grid isn’t just for pages! That is a common myth. Although it is certainly very useful for page layout, I find myself just as frequently reaching for grid when it comes to components. In this article I’ll address using CSS grid at the component level.

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Simple Interactive Pie Chart with CSS Variables and Houdini Magic

I got the idea for doing something of the kind when I stumbled across this interactive SVG pie chart. While the SVG code is as compact as it gets (a single <circle></circle> element!), using strokes for creating pie chart slices is problematic as we run into rendering issues on Windows for Firefox and Edge. Plus, in 2018, we can accomplish a lot more with a lot less JavaScript!

I managed to get the following result using a single HTML element for the chart and very little JavaScript. The future should completely eliminate the need for any JavaScript, but more on that later.

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1 Element CSS Rainbow Gradient Infinity

I first got the idea to CSS something of the kind when I saw this gradient infinity logo by Infographic Paradise. The gradient doesn't look like in the original illustration, as I chose to generate the rainbow logically instead of using the Dev Tools picker or something like that, but other than that, I think I got pretty close—let's see how I did that!

Dark theme in a day

Marcin Wichary has written a great piece that dives into how he used CSS Variables to create a night mode and high contrast theme in an app. There’s so many neat tricks about how to use CSS Variables (Chris has also looked at theming) as well as how to organize them (Andras Galante has an interesting take on this) in here. Plus, Marcin shares some tricks about using filters to invert the color of an image.

I also also love this part of the article where Marcin writes:

I was kind of amazed that all of this could happen via CSS and CSS alone: the colours, the transitions, the vectors, and even the images...

CSS is mighty powerful these days, and it’s posts like Marcin’s that remind me it wasn’t that long ago that theming an app like this would’ve been impossible.

A Strategy Guide To CSS Custom Properties

CSS preprocessor variables and CSS custom properties (often referred to as "CSS variables") can do some of the same things, but are not the same.

Practical advice from Mike Riethmuller:

If it is alright to use static variables inside components, when should we use custom properties? Converting existing preprocessor variables to custom properties usually makes little sense. After all, the reason for custom properties is completely different. Custom properties make sense when we have CSS properties that change relative to a condition in the DOM — especially a dynamic condition such as :focus, :hover, media queries or with JavaScript.

CSS Environment Variables

We were all introduced to the env() function in CSS when all that drama about "The Notch" and the iPhone X was going down. The way that Apple landed on helping us move content away from those "unsafe" areas was to provide us essentially hard-coded variables to use:

padding: 
  env(safe-area-inset-top) 
  env(safe-area-inset-right) 
  env(safe-area-inset-bottom) 
  env(safe-area-inset-left);

Uh ok! Weird! Now, nine months later, an "Unofficial Proposal Draft" for env() has landed. This is how specs work, as I understand it. Sometimes browser vendors push forward with stuff they need, and then it's standardized. It's not always waiting around for standards bodies to invent things and then browser vendors implementing those things.

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What Houdini Means for Animating Transforms

I've been playing with CSS transforms for over five years and one thing that has always bugged me was that I couldn't animate the components of a transform chain individually. This article is going to explain the problem, the old workaround, the new magic Houdini solution and, finally, will offer you a feast of eye candy through better looking examples than those used to illustrate concepts.

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