JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/sha1.js"></script>
<input type="text" id="in">

<input type="text" id="out">

CSS

body {
    padding: 20px 15px;
}
input, textarea {
    display: block;
    font-family: Consolas, monospace;
    border: 1px solid #dcdcdc;
    border-radius: 2px;
    padding: 5px 10px;
    width: 100%;
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    color: #444;
    font-size: 12px;
    margin-bottom: 15px;
}

JavaScript

function handler() {
    document.querySelector('#out').value = CryptoJS.SHA1(this.value);
}

var input = document.querySelector('#in');
input.addEventListener('keyup', handler);
input.addEventListener('change', handler);