JSFiddle - React, Tailwind, and code Playground

HTML

<div id="d"></div>
<button id="per">100%</button>
<button id="px">100px</button>

CSS

#d {
    height: 50px;
    width: 100px;
    background: #f00;
}

JavaScript

$('#per').click(function(){
    $('#d').css('width', 100 + '%')
})

$('#px').click(function(){
    $('#d').css('width', 100)
})