JSFiddle - React, Tailwind, and code Playground

HTML

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

Username: <input type="text" value="Testing" 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 usr = document.login.usr.value;
alert(usr);