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 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 JavaScript 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.