css and javascript performance tips
Post on 28-Jan-2015
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TOP CSS AND JAVASCRIPT PERFORMANCE TIPS
There are many risks that come with having a site that’s slow to load. You could risk losing
potential customers, have a lower engagement level and eventually end up with no traffic
whatsoever. The speed of a website is much more than just the size of files. Browsers need to
have the adequate capabilities to understand and process the code written.
Sometimes making edits to your code during the website development stage can be worthwhile
as they save the end-user time when trying to access your webpage, as browsers will be able to
digest and translate it quicker. Below are some key tips that web development
agency professionals should consider for speeding up the performance of their developments
through code.
Never Repeat
Make use of the cascade and never repeat code, unless absolutely necessary. It extends further
than simply using common classes; you should also make use of the heritance. In the same vein
you can use the same set of properties for multiple elements of your development ensuring you
separate multiple selectors using commas as usual.
JavaScript also allows you to make use of objects, functions and plugins which gives you even
less need to repeat code.
Utilise IDs
IDs are really fast and wherever possible you should make use of them. They are faster in both
CSS and JavaScript and when using JavaScript you can even use alternatives to jQuery to select
tags such as document.body.
Right to Left
Browsers translate and process jQuery and CSS from right to left. Therefore, where possibly
write in this way to speed things up for the browser. The only answer is to write your code as
specifically as possible and where possible write backwards, so the browser can digest and
translate what you’re trying to say in its natural way as quickly as possible.
Short Selectors
In some instances an extra item in your selector can completely ruin your code. For example if
you’re writing a “ul li a” selector in most instances it’s more than possible to simply use the “ul
a” for the same effect.
When it comes to JavaScript we’d recommend you simply don’t use it as all it will do is cost you
development time, user performance results and maintenance, as well as causing issues with
some browser compatibility.
Redefine Vars Locally
Many website developers simply skip the var declaration step altogether. It’s not ideal as you
end up creating a lot of global variables which can break other functionality and when the
browser tries to recover it will search locally then globally.
Even if you choose to use global scope vars you should consider redefining them locally to save
some time.
One Less JPG
The One Less JPG movement suggests a solution to the JaveScript library / framework size
problem. It simply states you should remove one .jpg file from your site to compensate for added
JavaScript. The removal of a single image can create the additional speed and space for your
JavaScript.
These tips will help ensure all your website development projects are completed with all
browsers in mind and with performance speed as a key focus.
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