How to center the JavaScript alert message box?

JavascriptWeb DevelopmentFront End Technology

To center the JavaScript alert box, you need to use the custom alert box. Under that, style it accordingly and position it to the center. Use the “top” and “left” CSS properties to achieve this. Set them as 50%, but as you can see the button below, so the property to 40% for correct alignment.


Live Demo

<!DOCTYPE html>
      <script src=""></script>
         function functionAlert(msg, myYes) {
            var confirmBox = $("#confirm");
            confirmBox.find(".yes").unbind().click(function() {
         #confirm {
            display: none;
            background-color: #F3F5F6;
            color: #000000;
            border: 1px solid #aaa;
            position: fixed;
            width: 300px;
            height: 100px;
            left: 50%;
            margin-left: -100px;
            padding: 10px 20px 10px;
            box-sizing: border-box;
            text-align: center;
         #confirm button {
            background-color: #FFFFFF;
            display: inline-block;
            border-radius: 12px;
            border: 4px solid #aaa;
            padding: 5px;
            text-align: center;
            width: 60px;
            cursor: pointer;
         #confirm .message {
            text-align: left;
      <div id="confirm">
         <div class="message">This is a warning message.</div>
            <button class="yes">OK</button>
      <input type="button" value="Click Me" onclick="functionAlert();" />
Published on 03-Feb-2018 14:09:43