Custom JavaScript Alert

custom-alert.css

/*
 * Basic style to the custom alert.
 * Customize it to your personal use.
 */
 
.alert-wrap {
    position: fixed;
    top: 0;
    left: 0;
    z-index: 2147483647; /* maximum value for a 32bit integer */
    display: none;
    width: 100%;
    height: 100%;
    background: rgba(0,0,0,0.5);
}

.alert-box {
    position: fixed;
    top: 20%;
    left: calc(50% - 150px);
    width: 300px;
}

.alert-box p {
    text-align: center;
}

.alert-box .close {
    -webkit-appearance: none;
}

custom-alert.html

<button id="test" onclick="alert('Test alert');">Click me</button>

<!-- add the following in the end of html document -->
<div class="alert-wrap">
    <div class="alert-box">
        <!-- do not remove the p tag. the alert message goes inside it -->
        <p></p>
        <button class="close">Close</button>
    </div>
</div>

custom-alert.js

(function($) {
    var alertWrap = $('.alert-wrap'),
        closeAlert = alertWrap.find('.close');

    window.alert = function(message) {
        alertWrap.find('p').text(message);
        alertWrap.fadeIn();
    }

    /*
     * the function below makes the .close button useless
     * closing the alert after clicking on any place
     */
    alertWrap.on('click', function() {
        $(this).fadeOut(function() {
            $(this).find('p').text('');
        });
    });
})(jQuery);