HTML Code

<!DOCTYPE html>

<html lang="en">

<head>

  <meta charset="utf-8">

  <title>Case sensitivity demo</title>

  <style>

    body { font-family: sans-serif; padding: 16px; }

    #output { margin-top: 12px; padding: 12px; background: #fef3c7; border: 1px solid #f59e0b; }

  </style>

</head>

<body>

  <p>Author: John Resig</p>

  <div id="output"></div>

  <script src="https://code.jquery.com/jquery-3.7.1.min.js"></script>

  <script>

    var upper = $("p:contains('John')").length;

    var lower = $("p:contains('john')").length;

    $("#output").html(

      "Upper (John): " + upper + "<br>Lower (john): " + lower

    );

    console.log("Upper:", upper, "Lower:", lower);

  </script>

</body>

</html>

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Case-sensitive :contains() (Try It)