{"id":9661,"date":"2021-01-13T16:03:48","date_gmt":"2021-01-13T16:03:48","guid":{"rendered":"http:\/\/www.max-sperling.bplaced.net\/?p=9661"},"modified":"2024-02-16T10:49:12","modified_gmt":"2024-02-16T10:49:12","slug":"how-gets-a-webpage-loaded","status":"publish","type":"post","link":"http:\/\/www.max-sperling.bplaced.net\/?p=9661","title":{"rendered":"Loading order of a webpage"},"content":{"rendered":"

Basics<\/strong><\/p>\n

1. Fetch the requested HTML file (via HTTP GET).
\n2. Parse (creating the DOM) that file (using DFS).
\n3. Fetch every found linked item (e.g. IMG, CSS, JS) on the way.1<\/sup>
\n4. Send DOMContentLoaded event after the DOM parsing is done.
\n5. Send window.onload event after everything is renderable.2<\/sup>
\n6. Generate the layout and paint the web page.<\/p>\n

1<\/sup> IMG and CSS are getting fetched in parallel, but JS blocks the DOM parsing.3<\/sup>
\n2<\/sup> All IMG and CSS files has been fetched and the CSSOM has been parsed.
\n3<\/sup> That isn’t true if the JS file is linked with a keyword (async\/defer)<\/a>.<\/p>\n

\n

Example<\/strong> (with async loaded JS)<\/p>\n

\r\n<html>\r\n  <head>\r\n    <link rel="stylesheet" href="style.css">\r\n    <script src="time.js" async><\/script>\r\n  <\/head>\r\n  <body>\r\n    <h1>Birubi Beach<\/h1>\r\n    <img src="http:\/\/www.max-sperling.bplaced.net\/wp-content\/uploads\/2020\/04\/Header_progressive.jpg" \/>\r\n    <h4 id="currentTime"><\/h4>\r\n  <\/body>\r\n<\/html>\r\n<\/pre>\n
\r\nbody {\r\n  text-align: center;\r\n  background-color: grey;\r\n}\r\n<\/pre>\n
\r\nfunction writeTime()\r\n{\r\n  document.getElementById("currentTime").innerHTML = new Date().toLocaleTimeString();\r\n}\r\nsetInterval(writeTime, 1000);\r\n<\/pre>\n
Analysis<\/u> (with DevTools, “Performance” tab)<\/p>\n
<\/a><\/p>\n
\r\nDCL ... DOMContentLoaded Event\r\nL   ... Onload Event\r\nFP  ... First Paint\r\nFCP ... First Contentful Paint\r\nLCP ... Largest Contentful Paint\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
Basics 1. Fetch the requested HTML file (via HTTP GET). 2. Parse (creating the DOM) that file (using DFS). 3.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"inline_featured_image":false},"categories":[55],"tags":[],"_links":{"self":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/9661"}],"collection":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=9661"}],"version-history":[{"count":1,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/9661\/revisions"}],"predecessor-version":[{"id":16841,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=\/wp\/v2\/posts\/9661\/revisions\/16841"}],"wp:attachment":[{"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=9661"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=9661"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.max-sperling.bplaced.net\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=9661"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}