现场演示：我的 HTML 文档

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="utf-8">
 <title>JavaScript Automatic Data Type Conversions</title>
</head>
<body>
 <script>
 document.write("3" - 2); // Prints: 1
 document.write(" ");
 
 document.write("3" + 2); // Prints: "32" (because + is also concatenation operator)
 document.write(" ");
 
 document.write(3 + "2"); // Prints: "32"
 document.write(" ");
 
 document.write("3" * "2"); // Prints: 6
 document.write(" ");
 
 document.write("10" / "2"); // Prints: 5
 document.write(" ");
 
 document.write(1 + true); // Prints: 2 (because true is converted to 1)
 document.write(" ");
 
 document.write(1 + false); // Prints: 1 (because false is converted to 0)
 document.write(" ");
 
 document.write(1 + undefined); // Prints: NaN
 document.write(" ");
 
 document.write(3 + null); // Prints: 3 (because null is converted to 0)
 document.write(" ");
 
 document.write("3" + null); // Prints: "3null"
 document.write(" ");
 
 document.write(true + null); // Prints: 1
 document.write(" ");
 
 document.write(true + undefined); // Prints: NaN
 </script>
</body>
</html>