Defer loading of JavaScript is one of the mostly used techniques for defer parsing of JavaScript which is done to improve the downloading speed of a website. This sentence though will be understood by some having a sound technical base, will yet be difficult for others. Even those who have their business websites like eCommerce websites, don’t understand much about the usage of JavaScript and what do if problems are faced with it. Hence a detailed or at least an introduction is required for all involved with websites. JavaScript is an interpreted programming language, originally developed for the web browsers for the client side scripts to have interaction with the user, to control the web browser, to alter the displayed document content, etc. As a prototype based scripting language, JavaScript is weakly typed, dynamic with first class functions.Image may be NSFW.
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JavaScript enhances the functions and therefore the appeal of a website to the users. Especially for websites full of content, it becomes difficult to navigate to the next page. JavaScript makes it easy to redirect or navigate to the next page for these websites based on HTML. It also shows the user’s time on the web page, timeout of the page, several popups, flying text, tooltips, scrolling banners, embedded audio and more. It gives a dynamic and attractive look to the website with the buttons it supports. JavaScript also improves user interactivity and vastly use while web designing is going on for a website.
However with so many positive things, JavaScript also has one negative side. JavaScript is known for taking making the downloading speed of the web page very slow. It happens because of the limited downloading capacity of the web browsers for scripts. In case of newer versions this downloading capacity is 6 scripts whereas the older ones can’t take beyond 2. Hence for websites having 10 or more plugins (if each plugin requires JavaScript), the time to download the entire website will be larger and thus the site becomes very slow. Also the JavaScript is there in the header which is why everything below the header takes time till the initial download of the page is done. Another thing is that search engines cannot easily navigate the text based web pages because of this scripting languages and thus hampering Search Engine Optimization venture for any site.
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Now this is solved by a few ways like removing additional scripts, minification of the files for better speed, downloading JavaScript files from sources like Google Library. Another step is defer loading of JavaScript functions which if not done will reduce the downloading size. Scripts has to be downloaded, executed and parsed (i.e. rightly analyzed) prior to the browsers rendering of that web page. By deferring loading of the JavaScript in the web page, the delay in the critical path i.e. the time taken to load for the startup of the main or home page of the website will become much less. It works by reducing the entire payload of the JS but will to some extent reduce the total number of bytes required for loading the initial pages and let the remaining bytes to get loaded itself. Hence webmasters prefer to have this process applied for the issue related to JavaScript for enabling quality SEO service for any site. Once it is solved, the web pages are then much easy to download on any web browser and easily navigable by the Search engines as well.
