<script async > vs document.getElementsByTagName('script')[0].insertBefore 等等？

Question

在

之间有什么material区别吗？

<script type="text/javascript" src="/script.js" async></script>

和

(function() {
  var s = document.createElement('script'); 
  s.type = 'text/javascript'; 
  s.async = true; 
  s.src = 'script.js'; 
  var x = document.getElementsByTagName('script')[0]; 
  x.parentNode.insertBefore(s, x)
;})();

?

Answer 1

我只能引用MDN:

In older browsers that don't support the async attribute, parser-inserted scripts block the parser; script-inserted scripts execute asynchronously in IE and WebKit, but synchronously in Opera and pre-4.0 Firefox.

所以换句话说，第二个仍然会在旧的 IE 和 WebKit 浏览器中异步评估脚本。

<script async > vs document.getElementsByTagName('script')[0].insertBefore 等等？

<script async > vs document.getElementsByTagName('script')[0].insertBefore etc.?

html

javascript

dom

pageload