Use sign and abs functions in CSS
npm install @csstools/postcss-sign-functionsnpm install @csstools/postcss-sign-functions --save-dev
[PostCSS Sign Functions] lets you use the sign and abs functions, following the [CSS Values 4] specification.
``css
.sign {
z-index: sign(-10px);
}
.sign {
z-index: sign(0);
}
.sign {
z-index: sign(10px);
}
.abs {
z-index: abs(-10px);
}
.abs {
z-index: abs(0);
}
.abs {
z-index: abs(10px);
}
.abs {
z-index: abs(10%);
}
/ becomes /
.sign {
z-index: -1;
}
.sign {
z-index: 0;
}
.sign {
z-index: 1;
}
.abs {
z-index: 10px;
}
.abs {
z-index: 0;
}
.abs {
z-index: 10px;
}
.abs {
z-index: max((10%), -1 * (10%));
}
`
> [!NOTE]
> The utility of static fallbacks for sign and abs is limited.%
> The most interesting values are variables and dynamic values (e.g. those containing ).
> It is impossible to generate static fallbacks in a build process for values that are dynamic on the client.
Add [PostCSS Sign Functions] to your project:
`bash`
npm install postcss @csstools/postcss-sign-functions --save-dev
Use it as a [PostCSS] plugin:
`js
const postcss = require('postcss');
const postcssSignFunctions = require('@csstools/postcss-sign-functions');
postcss([
postcssSignFunctions(/ pluginOptions /)
]).process(YOUR_CSS /, processOptions /);
`
Given the dynamic nature of custom properties it's impossible to know what the variable value is, which means the plugin can't compute a final value for the stylesheet.
Because of that, any usage that contains a var is skipped.
The preserve option determines whether the original notation
is preserved. By default, it is not preserved.
`js`
postcssSignFunctions({ preserve: true })
`css
.sign {
z-index: sign(-10px);
}
.sign {
z-index: sign(0);
}
.sign {
z-index: sign(10px);
}
.abs {
z-index: abs(-10px);
}
.abs {
z-index: abs(0);
}
.abs {
z-index: abs(10px);
}
.abs {
z-index: abs(10%);
}
/ becomes /
.sign {
z-index: -1;
z-index: sign(-10px);
}
.sign {
z-index: 0;
z-index: sign(0);
}
.sign {
z-index: 1;
z-index: sign(10px);
}
.abs {
z-index: 10px;
z-index: abs(-10px);
}
.abs {
z-index: 0;
z-index: abs(0);
}
.abs {
z-index: 10px;
z-index: abs(10px);
}
.abs {
z-index: max((10%), -1 * (10%));
z-index: abs(10%);
}
``
[cli-url]: https://github.com/csstools/postcss-plugins/actions/workflows/test.yml?query=workflow/test
[css-url]: https://cssdb.org/#sign-functions
[discord]: https://discord.gg/bUadyRwkJS
[npm-url]: https://www.npmjs.com/package/@csstools/postcss-sign-functions
[PostCSS]: https://github.com/postcss/postcss
[PostCSS Sign Functions]: https://github.com/csstools/postcss-plugins/tree/main/plugins/postcss-sign-functions
[CSS Values 4]: https://drafts.csswg.org/css-values-4/#sign-funcs