index.js

var postcss = require('postcss')
var pxtorem = require('postcss-pxtorem')

const PLATFORM = {
    WEAPP: 'weapp',
    H5: 'h5'
}

const DEVICE_RATIO = {
    '640': 2.34 / 2,
    '750': 1,
    '828': 1.81 / 2
}

const DEFAULT_H5_OPTIONS = {
    platform: 'h5',
    designWidth: 750,
    rootValue: 40,
    propList: ['*'] // enable all properties
}

const DEFAULT_WEAPP_OPTIONS = {
    platform: 'weapp',
    designWidth: 750,
    rootValue: 1,
    propList: ['*'] // enable all properties
}

module.exports = postcss.plugin('postcss-pxtransform', function (opts) {

    opts = opts || DEFAULT_WEAPP_OPTIONS

    return function (root, result) {
        switch (opts.platform) {
            case PLATFORM.WEAPP:
                return dealWithWeapp({root, result, opts})
            case PLATFORM.H5:
                return dealWithH5({root, result, opts})
        }
    }
})

function dealWithWeapp ({root, opts, result}) {
    opts = Object.assign({}, DEFAULT_WEAPP_OPTIONS, opts)
    var css = postcss(pxtorem(opts)).process(root.toResult()).css
    var cssRoot = postcss.parse(css)
    root.nodes = cssRoot.nodes

    root.walkDecls(function (decl) {
        let value = decl.value
        value = value.replace(/([0-9.]+)rem/ig, function (match, size) {
            return Math.ceil(size / DEVICE_RATIO[opts.designWidth] *
                10000) / 10000 + 'rpx'
        })
        decl.value = value
    })
}

function dealWithH5 ({root, result, opts}) {
    opts = Object.assign({}, DEFAULT_H5_OPTIONS, opts)
    var css = postcss(pxtorem(opts)).process(root.toResult()).css
    var cssRoot = postcss.parse(css)
    root.nodes = cssRoot.nodes
}