JSFiddle - React, Tailwind, and code Playground

by Paulpro

HTML

<ul class="month-wrapper">
    <li>Test</li>
</ul>
<ul class="year-wrapper">
    <li>Test</li>
</ul>

CSS

ul.month-wrapper li
{
    font-size: 13px;
    background-color: #0FF;
}
ul.year-wrapper li
{
    font-size: 16px;
    background-color: #FF0;
}

JavaScript

var MonthWidth = 30;
var YearWidth = MonthWidth * 12;

var ss = document.styleSheets[0];
if(ss.insertRule){
    ss.insertRule('ul.month-wrapper li {width: '+MonthWidth + 'px }', ss.cssRules.length);
    ss.insertRule('ul.year-wrapper li {width: '+YearWidth + 'px }', ss.cssRules.length);
}else if(ss.addRule){ // For IE only
    ss.addRule('ul.month-wrapper li', 'width: '+MonthWidth + 'px');
    ss.addRule('ul.year-wrapper li', 'width: '+YearWidth + 'px');
}