xxxxxxxxxx<html><head><meta charset="utf-8"><title>W3Cschool教程(w3cschool.cn)</title></head><body><p>设置参数的默认值。</p><p id="demo"></p><script>function myFunction(x, y) { if (y === undefined) { y = 0; } return x * y;}document.getElementById("demo").innerHTML = myFunction(4);</script></body></html>