In this Hasty Treat, Scott and Wes talk about CSS nesting — what it is, when to use it, and why.

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Show Notes

04:22 - What is it?

• https://drafts.csswg.org/css-nesting-1/#nest-prefixed
• https://twitter.com/argyleink/status/1371874777548267520

06:02 - Why nest?

• Easier to read
• Easier to write
• Prevents refactoring errors, allows for dry-er code. No more typing a parent div 100 times, with a possibility of screwing it up.

08:13 - When to use nesting

• Nesting is often overused
• Only nest what you would have written un-nested with a short hand (e.g. don’t nest just for the sake of it)
  • .container .item {} .container .item a {}
• Use it for scoping

10:06 - Nesting prefixes

• In order to nest CSS, you must first start it with a nesting selector

.tweet { & > p { } &.media-included { color: green; } & + .tweet { } // sibling & p { } // descentang }

• Component-based — tweet, card, company, Link

article{ color: blue; & { color: red; } }

and must be the first child of a compound selector

12:44 - @nest rule / media queries

• Mostly just a visual way to show nested

.foo { display: grid; @media(orientation: landscape) { & { grid-auto-flow: column; } } } .foo { display: grid; @media (orientation: landscape) { & { grid-auto-flow: column; } @media (min-inline-size > 1024px) { & { max-inline-size: 1024px; } } } } /* equivalent to .foo { display: grid; } @media (orientation: landscape) { .foo { grid-auto-flow: column; } } @media (orientation: landscape) and (min-inline-size > 1024px) { .foo { max-inline-size: 1024px; } } */

16:30 - How to use nesting today

• Literally any CSS preprocessor
• PostCSS to use spec

Links

• Syntax 274: How does stuff get added to CSS? Adam Argyle answers!
• Sass
• PostCSS
• CSS Variables

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