源代码:
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Wfuyu教程(wfuyu.com)</title> </head> <body> <p>函数可以访问定义在函数外的变量：</p> <button type="button" onclick="myFunction()">点我</button> <p id="demo"></p> <script> var a = 4; function myFunction() { document.getElementById("demo").innerHTML = a * a; } </script> </body> </html>
运行结果：