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<!DOCTYPE html> <html> <body> <h1>JavaScript 运算符</h1> <p>x = 7，y = 8，计算 z = x + y，然后显示 z：</p> <p id="demo"></p> <script> var x = 7; var y = 8; var z = x + y; document.getElementById("demo").innerHTML = z; </script> </body> </html>