I've been looking into this kind of tool for a while, but none of them are quite right for my purpose. I don't want a tool that spits out just-the-CSS-that-is-used, I want a tool that shows me blocks of CSS that it thinks are NOT used - ideally after I've loaded a number of different pages in a browser.
My use-case is for analyzing a large, existing website that has many years of accumulating CSS, and getting a feel for which blocks of code can be safely eliminated.
I'm pretty sure what I'm after needs a full-blown DOM to work effectively - either with something like PhantomJS or even running as a Chrome Extension. So far I haven't seen anything that fits the bill.
I honestly think this needs to be a part of Chrome Dev Tools's profiler. Already it's able to record sessions that persist across page loads, and tracks what CSS selectors are applied and which properties are overridden. I don't think it's much of a stretch to add a feature like this.
Agreed! We need something that collects data from multiple pages as you browse through and use your site. At the end it gives you a table of all your classes that didn't match anything (with line number references to your css file).
Though you need to manually visit all those pages. And it wouldn't be easy to traverse DOM with those server side logic/condition.
IMHO, do it offline and out of browser would be easier. But I also think doing it directly with the codes can be hard too since there are so many way that those css will be added to templates.
I have used a Firefox extension called Dust-Me Selectors[1] which does this. It breaks your css into used and unused selectors, it can spider the site for you, or you can leave it running as you browse the site and it will work automatically. Definitely slows things down though while you're using it.
I built something like this at my old company. Scrape every tag on the current page, subtract this array of used tags against all the tags in the CSS. Didn't take too long to build.
The problem with the PurifyCSS approach, like so many before it, is that you cannot really do this accurately from the server. It has to be done in the browser.
Helium is a dev tool. It takes a list of sample urls from the developer because its presumed the engineer will be able to make the best choice as to pages that represent all the aspects of their site.
It will work in any web page regardless of framework, because ultimately its all just web pages.
Helium will find the actual style sheets loaded into each page, then at the end of the scan give you an accurate and realistic report of the css selectors that were not found anywhere in your site.
There are some minor limitations, such as the inability to test for user-interactions with pseudo selectors like :active, :focus, :hover, etc.
As a designer that would love this tool for the speed and cleanliness factor it would give, i have a few other Qs:
1. Does it spit out a css file or multiple css file I can use immediately? Can i actually amend a local document with it, or do I have to copy paste?
2. Does it give any critique on poor selector methods? Definitely have a few foolish ways of doing things that could be improved with a little bit of "hey...stop that" feedback, in my work
3. ??? PROFIIT
4. Can it give me a few stats on the css to benchmark it? You're already showing me the unused ccs selectors, can you present other data that you could present to your boss and say hey...look at this, this is why it's worth doing this stuff
5. Known browser issues highlighted. "Hey! In IE8...that div ACTUALLY does this". Also, heres how to fix it. Insta–contextual documentation. As I say that I realise I'm asking for Clippy back in a way so I shall bow out. Responsive design? worth thinking about...anyway!
Really interesting project! I'm going it use it this weekend and see how it goes :)
It doesn't modify your css files. That's your job. It gives you a report of unused selectors. It can't test pseudo selectors requiring human interaction.
For many reasons, namely that we've already solved most of these "problems" years ago with simple concepts like OOCSS, SMACSS, and BEM. I suggest taking a look at this rebuttal.
http://keithjgrant.com/posts/against-css-in-js.html
The reasons people are running into problems with global css scope is because they don't understand the basics of how to write effective and maintainable CSS. Seems like many front end devs nowadays grew up with css hand-holding libraries like bootstrap, and can't seem to wrap their heads around completely necessary things like taking account for CSS specificity and how the cascade works and how to use it to your advantage.
The methodology gives you the tools to have control over the cascade. You cannot avoid it entirely.
Edit: Also the point I was getting at was that cascade is a useful and powerful tool, just as the methodologies for controlling it are. We will also soon have a property that will eliminate the cascade entirely... all:unset;
I just think the problems and solutions listed in the talk are either non-problems or are things that could be solved in superior ways. And that it introduces more problems and limitations than it solves.
Inline styles are great, but they don't support basic features such as pseudo classes/elements, so even implementing simple components like buttons was cumbersome.
With latest version of webpack's css loader you get css scoping (you no longer need to add lengthy prefixes to all selectors) and you can also use additional loaders for post-processing your styles (we use a lot of postcss plugins such as autoprefixer).
There's another way besides inlining and requirejs. In cases where you're doing server-side programming anyway, you can just have the server inject view-specific <link> elements pointing to individual CSS files as needed - augmenting the site's core CSS file. The downside is more requests to fetch those files, but after the first time you can take advantage of the browser's cache. As long as you keep the number of extra CSS files reasonable, this method costs almost nothing.
A variant of this is where you compile one CSS file from many view-specific ones beforehand. The advantage is it'll speed up things on the client side and the programming overhead is relatively small if you're using something to generate CSS anyway.
> In that case, it's because code reusability becomes a pita and you bloat your JS.
Does it? Last time I had a bigish web project, I was starting to inline everything (CSS and Javascript), and had my backend language deal with DRY. It even solved the problem CSS people use CSS generators for. As a rule, both CSS and javascrit suck for organizing content.
But then, I declared that project dead, and didn't wait to see the consequences of organizing things this way. So, somebody may have a much clear understanding about why that's wrong.
This would miss the point. Sure, it would still lighten the css file downloaded by the client, but it would do nothing to clean up the source file developers work with and thus lighten their cognitive burden, which imo is more important.
Nice. But from the description, it apparently doesn't work if you construct class names by string manipulation (like "item_" + (selected ? "selected" : "")). Maybe you shouldn't do that anyway, though.
Linking some string hanging off some runtime object to its CSS class usage quickly runs into halting problem issues.
There are certainly some arguments to keeping class names as opaque magic strings, but given certain levels of dynamic complexity and the lack of tools like CSS class inheritance, naming policy is sometimes far cleaner and more manageable.
Also, there is a minor concern about false positives. If you have a class called "name" or something generic like that, the odds of that string appearing in non-CSS usage your source code is fairly high.
Yes! that is a great library. Unfortunately, that library does not automatically detect the classes used in JS. So we thought we could give it a try to make one that would detect classes used in JS by default
I _think_ it shouldn't be too much code.
For my rails project, I wrote a simple shell script[1] to get all unused css classes and remove it my hand in final step, to make sure i will not remove css classes that actually used (e.g pre-define and use in future, overriding of third party css class)
The script basically does:
1. Use REGEX match all css classes, `cat` into one place
2. Read the class line by line and search in html,js files to see if this css is used (even support #addClass from js)
2.1 it also supports several class adding styles e.g. class="abc", class: "abc", :class=> 'abc' or even "xxx" class in this: class="abc xxx ijk"
2.2 People even do this in js: $modal.append($('<div class="modal-close-icon"></div>')); and the REGEX can also detect this lol.
This setup is ideal IMO. Keep your existing files, like bootstrap, intact in case you ever DO use them but integrate this into your deploy process to do compression and minification prior to getting out to your server.
How do you do this for JavaScript?
In Java I used a mixture of static analysis[1] and code coverage[2] with great success. For JavaScript there seem to be many (dead) coverage tools but nothing comparable to UCDetector.
What is the actual performance advantage gained in contrast to a simple minifier?
Given today's CPU speeds, I think the only thing you can save with this tool is bandwidth on mobile and even with this, the effort is not always worth the resulting speed gains as mobile networks get faster and faster.
Ha! that's one way of putting it. Another use case would be if you were to use a CSS framework (Bootstrap, Foundation) and you don't utilize all of it (they are both ~6k line files)
My use-case is for analyzing a large, existing website that has many years of accumulating CSS, and getting a feel for which blocks of code can be safely eliminated.
I'm pretty sure what I'm after needs a full-blown DOM to work effectively - either with something like PhantomJS or even running as a Chrome Extension. So far I haven't seen anything that fits the bill.