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>