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 Global Variable</title>
</head>
<body>
    <script>
    var greet = "Hello World!";
 
    // Defining function
    function greetWorld() {
        document.write(greet);
    }
     
    greetWorld();  // Prints: Hello World!
    document.write("<br>");
    document.write(greet); // Prints: Hello World!
    </script>
</body>
</html>  