How to validate html textbox not to allow special characters and space?

html, javascript, textbox, validation

Solution

You may try to use this function:

<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title></title>
    <script type="text/javascript">
    function blockSpecialChar(e){
        var k;
        document.all ? k = e.keyCode : k = e.which;
        return ((k > 64 && k < 91) || (k > 96 && k < 123) || k == 8 || k == 32 || (k >= 48 && k <= 57));
        }
    </script>
</head>
<body>
    <form id="frm" runat="server">
      <input type="text" name="folderName"  onkeypress="return blockSpecialChar(event)"/>
    </form>
</body>
</html>

Problem

This is my html: ``` <input type="text" name="folderName"> ``` Here, I want to validate the textbox value by not allowing to key in special characters and space. But it should allow underscore. How to validate this textbox?

Original source