postcss-unit-processor

  

PostCSS plugin to process css unit.

Install

``shell
$ npm install postcss postcss-unit-processor --save-dev
`

Usage

Use the processor function provided by the user to process the CSS unit. The default processor function is not to do any processing.

$3

`js
var fs = require('fs');
var postcss = require('postcss');
var unitProcessor = require('postcss-unit-processor');
var css = fs.readFileSync('main.css', 'utf8');
var options = {
processor: (value, unit) => {
if (unit === 'px') {
return value / 2;
}
}
};
var processedCss = postcss(unitProcessor(options)).process(css).css;

fs.writeFile('main-new.css', processedCss, function (err) {
if (err) {
throw err;
}
console.log('New file written.');
});
`

$3

`js
// Only process rem units
unitProcessor({
processor: (value, unit) => value,
unitList: ['rem']
})

// Process all units except rem
unitProcessor({
processor: (value, unit) => value,
unitList: ['!rem']
})

// Process only rem and px units
unitProcessor({
processor: (value, unit) => value,
unitList: ['rem', 'px']
})
`

$3

Type: Object | Null
Default:
`js
{
processor: (value) => value,
unitPrecision: 5,
propList: ['*'],
unitList: ['*'],
selectorBlackList: [],
replace: true,
mediaQuery: false,
exclude: /node_modules/i,
customUnitList: []
}
`

- processor (Function) css unit processing function.
- The plugin will call this function when the conditions are met, and pass the following parameters:
- value (Number): Unit value.
- unit (String): The name of the unit.
- node (Object): Current postCSS node object.
- root (Object): postCSS node root object.
- The function return value:
- If the Number is returned, the unit value is directly replaced, and the unit name remains unchanged.
- If an object is returned, the value of the object replaces the value, and the unit replaces the name.
- unitPrecision (Number) The decimal numbers to allow the processed units to grow to.
- unitList (Array) The units that can be changed by the processor function.
- Values need to be exact matches.
- Use wildcard to enable all units. Example: ['']
- Use ! to not match a unit. Example: ['*', '!rem']
- Combine multiple units: ['rem', 'px', 'vw']
- propList (Array) The properties that can be changed by the processor function.
- Values need to be exact matches.
- Use wildcard to enable all properties. Example: ['']
- Use at the start or end of a word. (['position*'] will match background-position-y)
- Use ! to not match a property. Example: ['*', '!letter-spacing']
- Combine the "not" prefix with the other prefixes. Example: ['', '!font']
- selectorBlackList (Array) The selectors to ignore.
- If value is string, it checks to see if selector contains the string.
- ['body'] will match .body-class
- If value is regexp, it checks to see if the selector matches the regexp.
- [/^body$/] will match body but not .body
- replace (Boolean) Replace rules instead of adding fallbacks.
- mediaQuery (Boolean) Allow processor function in media queries.
- exclude (String, Regexp, Function) The file path to ignore.
- If value is string, it checks to see if file path contains the string.
- 'exclude' will match \project\postcss-unit-processor\exclude\path
- If value is regexp, it checks to see if file path matches the regexp.
- /exclude/i will match \project\postcss-unit-processor\exclude\path
- If value is function, you can use exclude function to return a true and the file will be ignored.
- the callback will pass the file path as a parameter, it should returns a Boolean result.
- function (file) { return file.indexOf('exclude') !== -1; }
- customUnitList (Array) List of custom units to process in addition to default units.
- Values should be strings representing unit names (e.g., ['dp', 'rpx']).
- Only non-empty strings containing letters and the percentage sign are accepted.
- Custom units are added to the default set of units like px, rem, vw, etc.

$3

`js
var gulp = require('gulp');
var postcss = require('gulp-postcss');
var autoprefixer = require('autoprefixer');
var unitProcessor = require('postcss-unit-processor');

gulp.task('css', function () {

var processors = [
autoprefixer({
browsers: 'last 1 version'
}),
unitProcessor({
processor: (value, unit) => {
if (unit === 'px') {
return value / 2;
}
}
})
];

return gulp.src(['build/css/*/.css'])
.pipe(postcss(processors))
.pipe(gulp.dest('build/css'));
});
`

#### Input/Output

`css
// input
h1 {
margin: 0 0 20px;
font-size: 32px;
line-height: 1.2;
letter-spacing: 1px;
}
// output
h1 {
margin: 0 0 10px;
font-size: 16px;
line-height: 1.2;
letter-spacing: 0.5px;
}
``