现场演示：我的 HTML 文档

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<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>JavaScript String Data Type</title>
</head>
<body>
    <script>
    // Creating variables
    var a = 'Hi there!';  // using single quotes
    var b = "Hi there!";  // using double quotes
    
    // Printing variable values
    document.write(a + "<br>");
    document.write(b);
    </script>
</body>
</html>