docs(daily-email): add yesterday's post

website/source/_daily_emails/2022-09-11.md

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+---
+title: "Custom styles in Tailwind CSS: `@apply`, `theme` or custom plugins"
+date: "2022-09-11"
+permalink: "/archive/2022/09/11/custom-styles-tailwind-css-apply-theme-custom-plugins"
+tags: ["tailwind-css"]
+---
+
+There are three ways to add custom styles to a Tailwind CSS project. As there have been [some recent tweets](https://twitter.com/adamwathan/status/1559250403547652097) around one of them - the `@apply` directive - I'd like to look at and give examples for each.
+
+## What is `@apply`?
+
+`@apply` is a PostCSS directive, provided by Tailwind, to allow re-using it's classes - either when extracting components or overriding third-party styles.
+
+The CSS file is the same as if you were writing traditional CSS, but rather than adding declarations to a ruleset, you use the `@apply` directive and specify the Tailwind CSS class names that you want to apply.
+
+For example:
+
+```css
+fieldset {
+  @apply bg-primary-dark;
+}
+```
+
+This is a simple example but it's easy to see how this could be used in ways that weren't intended and how edge-cases can be found.
+
+Adam said in a another tweet:
+
+> I estimate that we spend at least $10,000/month trying to debug extremely edge-case issues people run into by using `@apply` in weird ways.
+
+## Using the `theme` function
+
+As well as `@apply`, Tailwind also provides a `theme` function that you can use in your CSS file. This removes the abstraction of using the class names and adds the ability to retrieve values from the `theme` section of your tailwind.config.js file.
+
+```css
+fieldset {
+  backgroundColor: theme('colors.primary.dark');
+}
+```
+
+This seems to be the preferred approach over using `@apply`.
+
+## Creating a custom plugin
+
+The `theme` function is also available if you write a custom Tailwind CSS plugin:
+
+```javascript
+const plugin = require('tailwindcss/plugin')
+
+plugin(({ addBase, theme }) => {
+  addBase({
+    fieldset: {
+      backgroundColor: theme('colors.primary.dark'),
+    }
+  })
+})
+```
+
+This is an approach that I've used for [generic, open-source plugins](https://github.com/opdavies?tab=repositories&q=%23tailwindcss-plugin) but for project-specific styling, I've mostly used `@apply` or the `theme` function.
+
+That said, I like the modular architecture of having different custom plugins - especially if they're separated into their own files - and being able to easily toggle plugins by simply adding to or removing from the `plugins` array.
+
+I usually don't write many custom styles in a Tailwind project but I think that I'll focus on using the `theme` function going forward, either in a stylesheet or a custom plugin.