console 命令行工具 X clear
console
<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>

</head>
<body>
    <script type="text/javascript">
        document.write("Heather1"+"<br/>");
        function callAlert(){
            alert("Welcome2");      
        }
        window.onload = function(){
            alert("欢迎光临萌萌小店！")
        }
        window.onbeforeunload = function(event){
            var e = event || window.event;
            e.returnValue = "记得下次再来哦！";
        }
        </script>
        <button onclick="alert('Welcome1')">点击1</button>
        <button onclick="callAlert()">点击2</button>
</body>
</html>