console 命令行工具 X clear

console

document.write("welcome to JS ");
function callAlert(){
alert('我被点击了一下');
}

<
<!DOCTYPE html> 
<html>
<head>
    <meta charset="utf-8" />
    <title></title>
    <script>
        var a= 3;
        document.write(a);
    </script>
</head>
<body>
</body>
</html>