Why you shouldn't assume all users have JavaScript

Does everyone have JavaScript now? Not according to the UK Government.

A Government Digital Services (GDS) blog post reported that 1.1 per cent of its users (made up of the UK population at large) didn't receive JavaScript.

This was made up of 0.2 per cent of people whose browsers didn't support JavaScript or had explicitly disabled it, and a massive 0.9 per cent of users who had JavaScript enabled, but for some reason did not receive it successfully (perhaps their train went into a tunnel – it’'s happened to us all).

So, with any website, it's good to offer some baseline experience for users without JavaScript.

Another good reason to ensure your site works without JavaScript is that an empty page doesn't get a great deal of Google juice.

It's much better to ensure that the same content is available in the no-JavaScript version. OK, so apparently Google's spiders are smart enough to run JavaScript these days, but what about other web-crawling bots?

One last issue with rendering a page in the browser is the performance hit on first load. Instead of downloading some HTML and applying CSS to it, the browser has to also execute some JavaScript and then assemble the page.

This critical path to first load is further delayed as the browser usually begins downloading any inline images before render.

With JavaScript, it has to wait until after the page content has been appended to the DOM. You can read more about this right here.

Words: Josh Emerson

Josh is a front-end developer at Mendeley. This article was originally published in net magazine.

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