Set value if entered value is more than a {number}

I have a block, width and height of which I want user to set by entering a value in the input.

I also want the value of inputs not to be more than certain number. Seems like I can't get parseInt to work..

if (parseInt($("#stwidth").val(), 10) > 113) {
  $("#stwidth").val("113");
}

if (parseInt($("#stwidth").val(), 10) > 62) {
	$("#stheight").val("62");
  
}

$("#stwidth, #stheight").keyup(function () {
  $('.preview').css({width: $("#stwidth").val() + "mm", height: $("#stheight").val() + "mm"});
});

.preview {
    width: 55mm;
    height: 19mm;
    background: #fff;
    overflow: hidden;
    border: 2px solid #3e6eb0;
    margin: 50px 0;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="text" name="stwidth" id="stwidth" value="55" maxlength="3"> x 
<input type="text" name="stheight" id="stheight"  value="19" maxlength="2"> 

<div class="preview"></div>

Solution

What you're missing was using Jquery keyup event handler on document onload for those user inputs. Here I'm giving a working solution, it'll not allow the width to be greater than 113 and height to be greater than 62:

<html>

<head>
    <style>
        .preview {
            width: 55mm;
            height: 19mm;
            background: #fff;
            overflow: hidden;
            border: 2px solid #3e6eb0;
            margin: 50px 0;
        }
    </style>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
    <script>
        $(function() {
            $("#stwidth").keyup(function() {
                if (parseInt($("#stwidth").val(), 10) > 113) {
                    $("#stwidth").val("113");
                }
            });

            $("#stheight").keyup(function() {
                if (parseInt($("#stheight").val(), 10) > 62) {
                    $("#stheight").val("62");

                }
            });

            $("#stwidth, #stheight").keyup(function() {
                $('.preview').css({
                    width: $("#stwidth").val() + "mm",
                    height: $("#stheight").val() + "mm"
                });
            });
        });
    </script>
</head>

<body>
</body>
<input type="text" name="stwidth" id="stwidth" value="55" maxlength="3"> x
<input type="text" name="stheight" id="stheight" value="19" maxlength="2">

<div class="preview"></div>

</html>