JSFiddle - React, Tailwind, and code Playground

HTML

<div>
  <input type="number"/>
  <button>OK</button>
</div>

CSS

div
{
  display:flex;
  width:100px;
  position:relative;
  border:solid 1px #000;
}

input
{
  flex:1;
  display:block;
  border:none;
}