根据font size比率，批量转换css中的rem单位

tranform-rem-width-ratio.js

var css = require('css');
var fs = require('fs');

var sourceFile = 'style.css';
var content = fs.readFileSync('./' + sourceFile, 'utf-8');

var obj = css.parse(content);
var rawFontSize = 50;
var toFontSize = 20;

function transformRem(defin, declaration) {
    var paires = defin.split(" ");
    return paires.map(raw => {
        if(raw === 'auto') return raw
        var rawValue = parseFloat(raw.replace('rem', ''));
        var newValue = (rawFontSize / toFontSize) * rawValue
        var finalValue = newValue.toFixed(3)
        if(isNaN(finalValue)) return 0;
        console.log('rawValue', rawValue, 'newValue', newValue)
        return [finalValue, 'rem'].join('')
    }).join(" ")
}

obj.stylesheet.rules.map(_ => {
    if(_.type == 'rule') {
        _.declarations.map(declaration => {
            if(declaration.value && declaration.value.indexOf('rem') > -1) {
                 if(declaration.property === 'padding') {
                    console.log(declaration)
                }
                declaration.value = transformRem(declaration.value, declaration);
            }
            return declaration;
        })
    }
    return _;
})

var newContent = css.stringify(obj);
fs.writeFileSync('new_' + sourceFile, newContent)