js阻塞文檔渲染與解析那麼css呢?css
結論1、css:阻塞渲染,不阻塞dom解析html
<head> <script> document.addEventListener('DOMContentLoaded',function(){ alert(document.getElementById("myinput")) }) </script> <!-- <script src="http://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script>--> <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"> </head> <body> <input type="text" id="myinput" /> <span class="label label-default">Default</span> </body>
當css樣式還未加載完成的時候,初始的html文檔已經加載,解析完畢了jquery
結論2、css的加載阻塞後面加載npm
<head> <!--<script> document.addEventListener('DOMContentLoaded',function(){ alert(document.getElementById("myinput")) }) </script>--> <script src="http://libs.baidu.com/jquery/2.1.4/jquery.min.js"></script> <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/bootstrap@3.3.7/dist/css/bootstrap.min.css" integrity="sha384-BVYiiSIFeK1dGmJRAkycuHAHRg32OmUcww7on3RYdg4Va+PmSTsz/K68vbdEjh4u" crossorigin="anonymous"> <script> alert(1) </script> </head> <body> <input type="text" id="myinput" /> <span class="label label-default">Default</span> </body>
因爲js的性值,加載後當即執行,能夠判斷,css阻塞js的加載bootstrap