To set the width and height of an alert box in JavaScript, you need to use the custom alert box. This alert box is styled with CSS.
Set the width and height of the alert box using the following code, which uses jQuery, a JavaScript library −
Example
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js">
</script>
<script>
function functionAlert(msg, myYes)
{
var confirmBox = $("#confirm");
confirmBox.find(".message").text(msg);
confirmBox.find(".yes").unbind().click(function()
{
confirmBox.hide();
});
confirmBox.find(".yes").click(myYes);
confirmBox.show();
}
</script>
<style>
#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;
}
</style>
</head>
<body>
<div id="confirm">
<div class = "message">This is a warning message.</div><br>
<button class="yes">OK</button>
</div>
<input type="button" value="Click Me" onclick="functionAlert();" />
</body>
</html>