JSFiddle - React, Tailwind, and code Playground

HTML

<div class="loginbox" id="loginbox">
    <div class="loginbox_close" id="loginbox_close"></div>
    ...
    <input type="button" value="Login" class="btn_login">
</div>

CSS

.loginbox {
    width:164px;
    padding:10px 18px 14px 18px;
    border:1px solid #CCC;
    border-top:0px;
    position:absolute;
    margin-left:780px;
    background:#678;
    opacity:0.9;
    box-shadow:inset 20px 40px 80px 4px #789,0 2px 8px #ABC;
    margin-top:100px;
    }



.loginbox_close {
    width:20px;
    height:20px;
    float:right;
    background:#EEE;
    cursor:pointer;
    position:absolute;
    margin-left:150px;
    border:1px solid red;
    }

JavaScript

$('#loginbox').on('click', '#loginbox_close', function() {
        alert('test'); // does not fire in FF, however webkit browser work!
    });