xxxxxxxxxx<html><head><meta charset="utf-8"><title>W3Cschool教程(w3cschool.cn)</title></head><head></head><body><p id="demo"></p><p>开启调试工具，在代码执行到第三行前会停止执行。</p><script>var x = 15 * 5;debugger;document.getElementById("demo").innerHTML = x;</script></body></html>