JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <input>
</form>

CSS

input {            
    width: 250px;
    -webkit-transition: width 1s linear;
    -o-transition: width 1s linear;
    -ms-transition: width 1s linear;
    -moz-transition: width 1s linear;
}
input:focus {
    width: 500px;
}