JSFiddle - React, Tailwind, and code Playground

HTML

<div>
    <input type="text"/>
    <a href="#">Button</a>
</div>

CSS

div {
    background:#AAAAAA;
    width:100%;
    min-width:300px;
    max-width:600px;
    display: -webkit-flex;
}

input {
    -webkit-flex: 1;
}

a {
    margin:0 10px;
}