JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<p><label for="id_username">Username:</label> <input name="username" maxlength="30" autocapitalize="off" autocorrect="off" type="text" id="id_username" /></p>
<p><label for="id_password">Password:</label> <input autocapitalize="off" autocorrect="off" type="password" name="password" id="id_password" /></p>
<p class="form-actions">
<input type="submit" class="button-green" value="Log in" />
</p>
</form>

JavaScript

window.opener.postMessage(JSON.stringify({"instagram":"loaded"}), '*');