async和defer同时出现则只渲染async
以下内容defer最后展示
<html>
<head>
<script async src="./async.js"></script>
<script defer src="./defer.js"></script>
<script src="./default.js"></script>
<script async defer src="./async_defer.js"></script>
</head>
<body>
<h1>Hello World</h1>
</body>
</html>
async和defer不在内部script生效
以下内容按顺序展示
<html>
<head>
<script async>
console.log('async')
</script>
<script defer>
console.log('defer')
</script>
<script>
console.log('default')
</script>
<script async defer>
console.log('default')
</script>
</head>
<body>
<h1>Hello World</h1>
</body>
</html>
