HTML Code

<!DOCTYPE html>

<html lang="en">

<head>

  <meta charset="utf-8">

  <title>hasData side effect check</title>

  <style>

    body { font-family: sans-serif; padding: 16px; max-width: 560px; }

    #box { background: #fef3c7; padding: 10px; border-radius: 6px; }

    pre { background: #f1f5f9; padding: 12px; border-radius: 6px; font-size: 14px; }

    button { margin: 8px 8px 0 0; padding: 10px 16px; background: #6366f1; color: #fff; border: none; border-radius: 6px; cursor: pointer; }

  </style>

</head>

<body>

  <div id="box">Pristine target</div>

  <button type="button" id="check">Check with hasData</button>

  <button type="button" id="touch">Touch with jQuery.data()</button>

  <pre id="out">Click a button to compare.</pre>

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

  <script>

    var el = document.getElementById("box");

    $("#check").on("click", function() {

      $("#out").text(

        "jQuery.hasData(el) → " + jQuery.hasData(el) +

        "\n(No cache created by this check)"

      );

    });

    $("#touch").on("click", function() {

      jQuery.data(el);

      $("#out").text(

        "Called jQuery.data(el) with no key.\n" +

        "jQuery.hasData(el) → " + jQuery.hasData(el) +

        "\n(Cache may now exist even with no values set!)"

      );

    });

  </script>

</body>

</html>

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