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<!DOCTYPE html> <html> <head> <title>Custom Validation Rules Example</title> <script src="https://code.jquery.com/jquery-3.6.0.min.js"></script> <script src="https://cdn.jsdelivr.net/jquery.validation/1.19.3/jquery.validate.min.js"></script> <script> $(document).ready(function(){ $.validator.addMethod("username", function(value, element) { return this.optional(element) || /^[a-zA-Z0-9]+$/.test(value); }, "Username must contain only letters and numbers."); $("form").validate({ rules: { username: { required: true, username: true } }, submitHandler: function(form) { alert("Form validated successfully!"); form.submit(); } }); }); </script> </head> <body> <form> <input type="text" name="username" placeholder="Username"><br> <input type="submit" value="Submit"> </form> </body> </html>
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