index.js
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var postcss = require('postcss');
module.exports = postcss.plugin('postcss-media-minmax', function () {
return function(css) {
var feature_unit = {
'width': 'px',
'height': 'px',
'device-width': 'px',
'device-height': 'px',
'aspect-ratio': '',
'device-aspect-ratio': '',
'color': '',
'color-index': '',
'monochrome': '',
'resolution': 'dpi'
};
//支持 min-/max- 前缀的属性
var feature_name = Object.keys(feature_unit);
var step = .001; // smallest even number that won’t break complex queries (1in = 96px)
var power = {
'>': 1,
'<': -1
};
var minmax = {
'>': 'min',
'<': 'max'
};
function create_query(name, gtlt, eq, value, params) {
return value.replace(/([-\d\.]+)(.*)/, function (match, number, unit) {
var initialNumber = parseFloat(number);
if (parseFloat(number) || eq) {
// if eq is true, then number remains same
if (!eq) {
// change integer pixels value only on integer pixel
if (unit === 'px' && initialNumber === parseInt(number, 10)) {
number = initialNumber + power[gtlt];
} else {
number = Number(Math.round(parseFloat(number) + step * power[gtlt] + 'e6')+'e-6');
}
}
} else {
number = power[gtlt] + feature_unit[name];
}
return '(' + minmax[gtlt] + '-' + name + ': ' + number + unit + ')';
});
}
// 读取 media-feature
css.walkAtRules(function(rule, i) {
if (rule.name !== "media" && rule.name !== "custom-media") {
return
}
/**
* 转换 <mf-name> <|>= <mf-value>
* $1 $2 $3
* (width >= 300px) => (min-width: 300px)
* (width <= 900px) => (max-width: 900px)
*/
//取值不支持负值
//But -0 is always equivalent to 0 in CSS, and so is also accepted as a valid <mq-boolean> value.
rule.params = rule.params.replace(/\(\s*([a-z-]+?)\s*([<>])(=?)\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*\)/gi, function($0, $1, $2, $3, $4) {
var params = '';
if (feature_name.indexOf($1) > -1) {
return create_query($1, $2, $3, $4, rule.params);
}
//如果不是指定的属性，不做替换
return $0;
})
/**
* 转换 <mf-value> <|<= <mf-name> <|<= <mf-value>
* 转换 <mf-value> >|>= <mf-name> >|>= <mf-value>
* $1 $2$3 $4 $5$6 $7
* (500px <= width <= 1200px) => (min-width: 500px) and (max-width: 1200px)
* (500px < width <= 1200px) => (min-width: 501px) and (max-width: 1200px)
* (900px >= width >= 300px) => (min-width: 300px) and (max-width: 900px)
*/
rule.params = rule.params.replace(/\(\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*(<|>)(=?)\s*([a-z-]+)\s*(<|>)(=?)\s*((?:-?\d*\.?(?:\s*\/?\s*)?\d+[a-z]*)?)\s*\)/gi, function($0, $1, $2, $3, $4, $5, $6, $7) {
if (feature_name.indexOf($4) > -1) {
if ($2 === '<' && $5 === '<' || $2 === '>' && $5 === '>') {
var min = ($2 === '<') ? $1 : $7;
var max = ($2 === '<') ? $7 : $1;
// output differently depended on expression direction
// <mf-value> <|<= <mf-name> <|<= <mf-value>
// or
// <mf-value> >|>= <mf-name> >|>= <mf-value>
var equals_for_min = $3;
var equals_for_max = $6;
if ($2 === '>') {
equals_for_min = $6;
equals_for_max = $3;
}
return create_query($4, '>', equals_for_min, min) + ' and ' + create_query($4, '<', equals_for_max, max);
}
}
//如果不是指定的属性，不做替换
return $0;
});
});
}
});