Tailwindify props

Converts component and object properties to Tailwind classes.

npm i tailwindify-props

Basic usage

In your tailwind config, use the transform function so the classes generated by your props get picked up by Tailwind and end up in your css output.

import { svelte } from 'tailwindify-props/transform';

export default {
	content: {
		files: ['src/**/*.svelte'],
		transform: {
			svelte: svelte({
				replacers: {
					bg: 'bg-$value',
					text: 'text-$value',
					lineHeight: '6'
				}
			})
		}
	}
};

Then in your component, you can have props like this:

<script>
	export let text = 'blue-500';
</script>

<button class="text-{text}"> My button </button>

To output:

<button class="text-blue-500">My button</button>

.text-blue-500 {
	color: blue;
}

You can now modify this prop from outside:

<MyComponent text="red-800" />

<button class="text-red-800">My button</button>

.text-red-500 {
	color: red;
}

It also works with javascript/typescript objects and constants:

<script lang="ts">
	type ButtonStyle = {
		bg: 'black' | 'red';
		text: 'white' | 'blue';
	};

	export let styles: ButtonStyle = {
		bg: 'black',
		text: 'white'
	};

	const lineHeight = '6';
</script>

<button class="bg-{styles.bg} text-{styles.text} leading-{lineHeight}"> My button </button>

<button class="leading-6 bg-black text-white">My button</button>

.bg-black {
	background-color: black;
}

.text-white {
	color: white;
}

.leading-6 {
	line-height: 1.5;
}

The transform function

You can import transform functions from tailwindify/transform. The function has the name of the file extension you want to transform. You can then use it in the content.transform property of your Tailwind config.

Right now, only Svelte is supported.

import { svelte } from 'tailwindify-props/transform';

export default {
	content: {
		files: ['src/**/*.svelte'],
		transform: {
			svelte: svelte()
		}
	}
};

The transform function accepts the following config object:

type Config = {
	replacers: {
		[key: string]: string | (value: string, prop: string) => string;
	};
	defaultScreen?: string;
	ignoredAttributes?: (string | RegExp)[];
};

Replacers

Replacers correspond to the props you want to convert to Tailwind classes.

The key is the prop name.

The value can either be a string or a function that returns a string. This allows you to format the resulting class however you like. The '$value' part of the string will be replaced with the actual value.

By default, all props are converted to the format '$prop-$value'. Sometimes that's good, but oftentimes this results in the wrong class name. For exemple, borderColor prop with a value of 'red' will generate the class borderColor-red. You can override this behavior by specifying a replacer for borderColor.

export default {
	content: {
		transform: {
			svelte: svelte({
				replacers: {
					borderColor: 'border-$value'
				}
			})
		}
	}
};

You can even use custom values and multiple classes for the same prop name.

export default {
	content: {
		transform: {
			svelte: svelte({
				replacers: {
					size: 'w-[$value] h-[$value]'
				}
			})
		}
	}
};

If you need more customization, you can pass a function instead. The function receives the value and the prop key as arguments and must return a string.

export default {
	content: {
		transform: {
			svelte: svelte({
				replacers: {
					mySpecialProp: (value, prop) => {
						if (Number(value) > 5) {
							return `custom-${value}`;
						}
						return `${prop}_${value}`;
					}
				}
			})
		}
	}
};

Responsive values

Passing a single value to our props is great, but what if you need responsive values?

You can chain multiple responsive values with the | separator and use your own Tailwind screen prefixes.

<MyButtonComponent padding="24|xs:32|lg:40" />

<button class="p-24 xs:p-32 lg:p-40">Click me!</button>

If you find yourself often using the same screen prefix, you can omit it.

<MyButtonComponent padding="24|32" />

<button class="p-24 xs:p-32">Click me!</button>

The default screen prefix is xs, but you can customize it in your Tailwind config:

export default {
	content: {
		transform: {
			svelte: svelte({
				defaultScreen: 'sm'
			})
		}
	}
};

Ignored attributes

Since the transform functions rewrite the code to generate the classes, some attributes may want to be ignored. The class attribute is always ignored by default, otherwise it would modify perfectly valid classes and Tailwind would not identify them. You can add other attributes to ignore, using either a string or a RegExp.

export default {
	content: {
		transform: {
			svelte: svelte({
				ignoredAttributes: ['klass', 'className', /ignore/gi]
			})
		}
	}
};

The tailwindify helper

Doing string interpolation to generate our classes isn't that complicated when you have simple values. But a value like this is more difficult to parse:

<MyComponent padding="24|28|sm:32|lg:40" />

To make this easier, you can use tailwindify to generate the classes.

type Tailwindify = (
	classPrefix: string | string[],
	values: string,
	defaultScreen: string
) => string;

<script>
import { tailwindify } from 'tailwindify-props';

export let padding = '24|28|sm:32|lg:40';
</script>

<div class="{tailwindify('p', padding)}"></div>

<div class="p-24 xs:p-28 sm:p-32 lg:p-40"></div>

You can generate multiple classes in the same function call:

<script>
import { tailwindify } from 'tailwindify-props';

export let size = '24|40';
</script>

<div class="{tailwindify(['w', 'h'], size)}"></div>

<div class="w-24 h-24 xs:w-40 xs:h-40"></div>

You can also specify a different default screen:

<script>
import { tailwindify } from 'tailwindify-props';

export let size = '24|40';
</script>

<div class="{tailwindify(['w', 'h'], size, 'sm')}"></div>

<div class="w-24 h-24 sm:w-40 sm:h-40"></div>

An additional benefit of using tailwindify is that you might not need to specify any replacers at all. The transform function will parse the code for any tailwindify calls and automatically generate replacers based on the arguments. For example, this code

<script>
import { tailwindify } from 'tailwindify-props';

export let size = '24|40';

const sizeClasses = tailwindify(['w', 'h'], size);
</script>

will generate the replacer

{
	size: 'w-$value h-$value';
}

and the classes 'w-24 xs:w-40 h-24 xs:h-40'.

If this format doesn't suit your needs, you can always specify a replacer for that prop and it will override the default.