<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="UTF-8">
<title>JS debugger调试</title>
</head>
<body>
<script type="text/javascript">
// A debugger statement can be placed anywhere in the procedure to abort execution. Using the debugger statement is similar to setting breakpoints in your code.
The //debugger statement aborts execution, but it does not close any files or clear any variables.
for(i = 1; i<5; i++) {
document.write(i);
debugger;
}
</script>
</body>
</html>
Reference link: http://www.w3cschool.cn/javascript/js-debugging.html
Effect picture: