twrnc
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4.2.0 • Public • Published

Tailwind React Native Classnames 🏄‍♂️

A simple, expressive API for TailwindCSS + React Native, written in TypeScript

import { View, Text } from 'react-native';
import tw from 'twrnc';

const MyComponent = () => (
  <View style={tw`p-4 android:pt-2 bg-white dark:bg-black`}>
    <Text style={tw`text-md text-black dark:text-white`}>Hello World</Text>
  </View>
);

👋 NB: v4.0.0 was just released! See migration guide for upgrading instructions.

Features 🚀

  • full support for all native RN styles with tailwind counterparts: (view, layout, image, shadow, and text).
  • very fast: best performance of all RN styling libraries, according to this benchmark.
  • compatible with Tailwind CSS v3 and v2
  • respects your tailwind.config.js for full configuration
  • platform prefixes: android:mt-4 ios:mt-2
  • dark mode support: bg-white dark:bg-black
  • media query support: w-48 lg:w-64 (also, arbitrary: min-w-[600px]:flex-wrap)
  • device orientation prefixes: portrait:flex-col landscape:flex-row
  • vw and vh unit support: h-screen, min-w-screen, w-[25vw], etc...
  • retina device pixel density prefix: w-4 retina:w-2
  • arbitrary, JIT-style classes: mt-[31px] bg-[#eaeaea] text-red-200/75, etc...
  • tagged template literal syntax for most common usage
  • merges supplied RN style objects for unsupported utilities or complex use cases
  • supports custom utility creation via standard plugin config.
  • flexible, conditional styles based on classnames package api.
  • written 100% in Typescript, ships with types

Docs:

Installation

npm install twrnc

API

The default export is an ES6 Tagged template function which is nice and terse for the most common use case -- passing a bunch of space-separated Tailwind classes and getting back a react-native style object:

import tw from 'twrnc';

tw`pt-6 bg-blue-100`;
// -> { paddingTop: 24, backgroundColor: 'rgba(219, 234, 254, 1)' }

In the spirit of Tailwindcss's intuitive responsive prefix syntax, twrnc adds support for platform prefixes to conditionally apply styles based on the current platform:

// 😎 styles only added if platform matches
tw`ios:pt-4 android:pt-2`;

Media query-like breakpoint prefixes supported (see Breakpoints for configuration):

// 😎 faux media queries
tw`flex-col lg:flex-row`;

Dark mode support (see here for configuration);

// 😎 dark mode support
tw`bg-white dark:bg-black`;

You can also use tw.style() for handling more complex class name declarations. The api for this function is directly taken from the excellent classnames package.

// pass multiple args
tw.style('text-sm', 'bg-blue-100', 'flex-row mb-2');

// arrays of classnames work too
tw.style(['text-sm', 'bg-blue-100']);

// falsy stuff is ignored, so you can do conditionals like this
tw.style(isOpen && 'bg-blue-100');

// { [className]: boolean } style - key class only added if value is `true`
tw.style({
  'bg-blue-100': isActive,
  'text-red-500': invalid,
});

// or, combine tailwind classes with plain react-native style object:
tw.style('bg-blue-100', { resizeMode: `repeat` });

// mix and match input styles as much as you want
tw.style('bg-blue-100', ['flex-row'], { 'text-xs': true }, { fontSize: 9 });

If you need some styling that is not supported in a utility class, or just want to do some custom run-time logic, you can pass raw RN style objects to tw.style(), and they get merged in with the styles generated from any other utility classes:

tw.style(`mt-1`, {
  resizeMode: `repeat`,
  width: `${progress}%`,
});
// -> { marginTop: 4, resizeMode: 'repeat', width: '32%' }

The tw function also has a method color that can be used to get back a string value of a tailwind color. Especially useful if you're using a customized color pallette.

tw.color('blue-100'); // `bg|text|border-blue-100` also work
// -> "rgba(219, 234, 254, 1)"

You can import the main tw function and reach for tw.style only when you need it:

import tw from 'twrnc';

const MyComponent = () => (
  <View style={tw`bg-blue-100`}>
    <Text style={tw.style('text-md', invalid && 'text-red-500')}>Hello</Text>
  </View>
);

...or if the tagged template function isn't your cup of tea, just import tw.style as tw:

import { style as tw } from 'twrnc';

const MyComponent = () => (
  <View style={tw('bg-blue-100', invalid && 'text-red-500')}></View>
);

Customization

You can use twrnc right out of the box if you haven't customized your tailwind.config.js file at all. But more likely you've got some important app-specific tailwind customizations you'd like to use. For that reason, we expose the ability to create a custom configured version of the tw function object.

// lib/tailwind.js
import { create } from 'twrnc';

// create the customized version...
const tw = create(require(`../../tailwind.config.js`)); // <- your path may differ

// ... and then this becomes the main function your app uses
export default tw;

...and in your component files import your own customized version of the function instead:

// SomeComponent.js
import tw from './lib/tailwind';

⚠️ Make sure to use module.exports = {} instead of export default {} in your tailwind.config.js file, as the latter is not supported.

Enabling Device-Context Prefixes

To enable prefixes that require runtime device data, like dark mode, and screen size breakpoints, etc., you need to connect the tw function with a dynamic source of device context information. The library exports a React hook called useDeviceContext that takes care of this for you. It should be included one time, at the root of your component hierarchy, as shown below:

import tw from './lib/tailwind'; // or, if no custom config: `from 'twrnc'`
import { useDeviceContext } from 'twrnc';

export default function App() {
  useDeviceContext(tw); // <- 👋
  return (
    <View style={tw`bg-white dark:bg-black`}>
      <Text style={tw`text-black dark:text-white`}>Hello</Text>
    </View>
  );
}

⚠️ If you're using Expo, make sure to make the following change in app.json to use the dark: prefix as Expo by default locks your app to light mode only.

{
  "expo": {
    "userInterfaceStyle": "automatic"
  }
}

Taking Control of Dark Mode

By default, if you use useDeviceContext() as outlined above, your app will respond to ambient changes in the device's color scheme (set in system preferences). If you'd prefer to explicitly control the color scheme of your app with some in-app mechanism, you'll need to configure things slightly differently:

import { useDeviceContext, useAppColorScheme } from 'twrnc';

export default function App() {
  useDeviceContext(tw, {
    // 1️⃣  opt OUT of listening to DEVICE color scheme events
    observeDeviceColorSchemeChanges: false
    // 2️⃣  and supply an initial color scheme
    initialColorScheme: `light`, // 'light' | 'dark' | 'device'
  });

  // 3️⃣  use the `useAppColorScheme` hook anywhere to get a reference to the current
  // colorscheme, with functions to modify it (triggering re-renders) when you need
  const [colorScheme, toggleColorScheme, setColorScheme] = useAppColorScheme(tw);

  return (
    {/* 4️⃣ use one of the setter functions, like `toggleColorScheme` in your app */}
    <TouchableOpacity onPress={toggleColorScheme}>
      <Text style={tw`text-black dark:text-white`}>Switch Color Scheme</Text>
    </TouchableOpacity>
  );
}

Customizing Breakpoints

You can customize the breakpoints in the same way as a tailwindcss web project, using tailwind.config.js. The defaults that ship with tailwindcss are geared towards the web, so you likely want to set your own for device sizes you're interested in, like this:

// tailwind.config.js
module.exports = {
  theme: {
    screens: {
      sm: '380px',
      md: '420px',
      lg: '680px',
      // or maybe name them after devices for `tablet:flex-row`
      tablet: '1024px',
    },
  },
};

Adding Custom Classes

To add custom utilities, use the plugin method described in the tailwind docs, instead of writing to a .css file.

const plugin = require('tailwindcss/plugin');

module.exports = {
  plugins: [
    plugin(({ addUtilities }) => {
      addUtilities({
        '.btn': {
          padding: 3,
          borderRadius: 10,
          textTransform: `uppercase`,
          backgroundColor: `#333`,
        },
        '.resize-repeat': {
          resizeMode: `repeat`,
        },
      });
    }),
  ],
};

Wil also allow you to supply a string of other utility classes (similar to @apply), instead of using CSS-in-JS style objects:

module.exports = {
  plugins: [
    plugin(({ addUtilities }) => {
      addUtilities({
        // 😎 similar to `@apply`
        '.btn': `px-4 py-1 rounded-full bg-red-800 text-white`,
        '.body-text': `font-serif leading-relaxed tracking-wide text-gray-800`,
      });
    }),
  ],
};

Matching Conditional Prefixes

twrnc also exposes a tw.prefixMatch(...prefixes: string[]) => boolean function that allows you to test whether a given prefix (or combination of prefixes) would produce a style given the current device context. This can be useful when you need to pass some primitive value to a component, and wish you could leverage tw's knowledge of the current device, or really anywhere you just need to do some logic based on the device context. This could also be accomplished by importing Platform or a combination of other RN hooks, but chances are you've already imported your tw function, and this saves you re-implementing all that logic on your own:

const SomeComponent = () => (
  <View>
    <Thumbnail imageSize={tw.prefixMatch(`portrait`) ? 60 : 90} />;
    {tw.prefixMatch(`ios`, `dark`) ? <CustomIosDarkModeThing /> : <Thing />}
  </View>
);

Box Shadows

Box shadows in CSS differ substantially from shadow in RN, so this library doesn't attempt to parse CSS box-shadow strings and translate them into RN style objects. Instead, it offers a number of low-level utilities not present in tailwindcss, which map to the 4 shadow props in RN:

// RN `shadowColor`
tw`shadow-white`; // > { shadowColor: `#fff` }
tw`shadow-red-200`; // > { shadowColor: `#fff` }
tw`shadow-[#eaeaea]`; // > { shadowColor: `#eaeaea` }
tw`shadow-black shadow-opacity-50`; // > { shadowColor: `rgba(0,0,0,0.5)` }

// RN `shadowOffset`
tw`shadow-offset-1`; // > { shadowOffset: { width: 4, height: 4 } }
tw`shadow-offset-2/3`; // > { shadowOffset: { width: 8, height: 12 } }
tw`shadow-offset-[3px]`; // > { shadowOffset: { width: 3, height: 3 } }],
tw`shadow-offset-[4px]/[5px]`; // > { shadowOffset: { width: 4, height: 5 } }],

// RN `shadowOpacity`
tw`shadow-opacity-50`; // { shadowOpacity: 0.5 }

// RN `shadowRadius`
tw`shadow-radius-1`; // { shadowRadius: 4 }
tw`shadow-radius-[10px]`; // { shadowRadius: 10 }

We also provide a default implementation of the shadow-<X> utils provided by tailwindcss, so you can use:

tw`shadow-md`;
/*
-> {
  shadowOffset: { width: 1, height: 1 },
  shadowColor: `#000`,
  shadowRadius: 3,
  shadowOpacity: 0.125,
  elevation: 3,
}
*/

To override the default implementations of these named shadow classes, add your own custom utilities -- any custom utilities you provide with the same names will override the ones this library ships with.

RN-Only Additions

twrnc implements all of the tailwind utilities which overlap with supported RN (native, not web) style props. But it also adds a sprinkling of RN-only utilities which don't map to web-css, including:

  • low-level shadow utilities
  • elevation (android only), eg: elevation-1, elevation-4
  • small-caps -> {fontVariant: 'small-caps'}
  • number based font-weight utilities font-100, font-400, (100...900)
  • direction-(inherit|ltr|rtl)
  • align-self: baseline; via self-baseline
  • include-font-padding and remove-font-padding (android only: includeFontPadding)
  • image tint color control (tint-{color} e.g. tint-red-200)

JIT-Style Arbitrary Values

Many of the arbitrary-style utilities made possible by Tailwind JIT are implemented in twrnc, including:

  • arbitrary colors: bg-[#f0f], text-[rgb(33,45,55)]
  • negative values: -mt-4, -tracking-[2px]
  • shorthand color opacity: text-red-200/75 (red-200 at 75% opacity)
  • merging color/opacity: border-black border-opacity-75
  • arbitrary opacity amounts: opacity-73
  • custom spacing: mt-[4px], -pb-[3px], tracking-[2px]
  • arbitrary fractional insets: bottom-7/9, left-5/8
  • arbitrary min/max width/height: min-w-[40%], max-h-3/8, w-[25vw], h-[21px]
  • arbitrary breakpoints: min-w-[600px]:flex-row, max-h-[1200px]:p-4

Not every utility currently supports all variations of arbitrary values, so if you come across one you feel is missing, open an issue or a PR.

VS Code Intellisense

Add the following to the settings of the official Tailwind plugin for VS Code.

// ...
"tailwindCSS.classAttributes": [
    // ...
    "style"
],
"tailwindCSS.experimental.classRegex": [
    "tw`([^`]*)",
    ["tw.style\\(([^)]*)\\)", "'([^']*)'"]
]

More detailed instructions, including how to add snippets, are available here.

Memo Busting

If you're using device-context prefixes (like dark:, and md:), memoized components can cause problems by preventing re-renders when the color scheme or window size changes. You may not be memoizing explicitly yourself as many third-party libraries (like react-navigation) memoizes their own components.

In order to help with this problem, twrnc exposes a .memoBuster property on the tw object. This string property is meant to passed as a key prop to break memoization boundaries. It is stable (preventing re-renders) until something in the device context changes, at which point it deterministically updates:

<SomeMemoizedComponent key={tw.memoBuster} />

This is not a perfect solution for all memoization issues. For caveats and more context, see #112.

Migrating from Previous Versions

See migration-guide.md.

Prior Art

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Install

npm i twrnc

Weekly Downloads

11,155

Version

4.2.0

License

MIT

Unpacked Size

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Total Files

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Collaborators

  • jaredhenderson