JSFiddle - React, Tailwind, and code Playground

HTML

<form method="post" id="login">

Username: <input type="text" value="sd" name="usr" />
Password: <input type="password" value="" name="pw"/>
<input type="submit" id="log" name="log" value="Login" style="width:250px;"/><br/>

</form>

JavaScript

var username = document.getElementsByName('usr')[0].value
alert(username);