Writing Good CSS

I’m always trying to learn new things. However, I also try to learn ways to improve the way I already do things. Both at my full-time gig and for client side-projects, the thing I’ve always wanted to improve on was my CSS. I’ve always felt I’m pretty good when it comes to CSS, but I’ve always found it messy to read, and often hard to maintain.

What I’ve been trying to do, is find out what makes good, readable, maintainable CSS. I think I’ve come up with (and found) some ways to make this all possible.

The Problems

There are several things that bother me about CSS. The most common annoyances I have are:

  • repeating common code
  • browser prefixes
  • lack of comments
  • over qualified selectors
  • poor class names

When it comes to my personal projects, I take full responsibility for my code. I rarely comment my CSS, and often treat it as an afterthought. That’s just wrong.

For a long time I figured that my class names are “semantic” and it’s just me doing things, so there’s no need to explain the code, or little “hacks”, or anything.

Coming back to code on a long-standing project quickly proves this theory to be very wrong.

When it comes to code at work, I can’t take all the blame. In fact, part of the issue is the number of people who have had their hands in there.Currently our team has seven of us who at some point have written CSS for our sites, with another 6-8 that have come and gone over the years. Each member of the team has varying levels of knowledge and ability regarding CSS.

As well, as is often the case with long-standing projects, some of the code is old. A lot of it is pre-CSS3, or pre-whatever-trend-was-cool-5-years-ago. In both cases, there were often different ways of doing things at the time it was written, and in some cases, a natural lack of knowledge.

I’ve also learned that some programmers will insist that their code is “self-documenting”. If you’re unfamiliar with that term, it translates to “my code has no comments”.

Solutions

While nothing is perfect, I believe there are things we can do to improve our code. I discovered CSS Guidelines by Harry Roberts a while back. Itt holds true to the promise of “High-level advice and guidelines for writing sane, manageable, scalable CSS”.

Comments

While CSS Guidelines gives specifics on comment styles, I personally just try to put something in to tell future me what I was thinking. I start every component with a comment representing the title, them details on the intent of the component.

When using a preprocessor I style specific comments to either be included with the CSS, or skipped by the preprocessor. I’m still working on this part, and trying to get into the habit of putting something, anything.

Object-orientation

Object-orientation is a programming paradigm that breaks big things into small things. From Wikipedia:

Object-oriented programming (OOP) is a programming paradigm that represents the concept of ‘objects’ […] which are usually instances of classes, [and] are used to interact with one another to design applications and computer programs.

When it comes to CSS, we call this object-oriented CSS, or OOCSS. The basic concept breaks apart the structure of the element, from the skin of the element. This means we can easily reuse any recurring design patterns, without necessarily reusing the specific implementation details at the same time. OOCSS focuses heavily on the reuse of code, which makes us faster, and can keep the size of our codebase down.

I think of structural aspects like skeletons; common frames that give constructs known as object. These objects are simple design patterns that are free from any cosmetics. We abstract the structure from a set of components in order to have a generic object.

We then optionally add the “skin” layer to our structure so we can give the abstractions a specific look and feel. For example (taken from CSS Guidelines):

/**
 * A simple, design-free button object. Extend this object with a `.btn--*` skin
 * class.
 */
.btn {
    display: inline-block;
    padding: 1em 2em;
    vertical-align: middle;
}

/**
 * Positive buttons' skin. Extends `.btn`.
 */
.btn--positive {
    background-color: green;
    color: white;
}

/**
 * Negative buttons' skin. Extends `.btn`.
 */
.btn--negative {
    background-color: red;
    color: white;
}

Here we see how the .btn class simply provides structure to an element, but has nothing concerning cosmetics. We can extend .btn with a second class, like .btn--positve to give that element more specific styling:

<button class="btn  btn--positive">OK</button>

I much prefer to use multiple classes in my HTML, over using something like @extend in a preprocessor. This gives me more visibility in my HTML allowing me to quickly see what classes are applied to my element. It also means that my classes are not tightly bound to other styles in my CSS. It sort of helps OOCSS following the concepts of encapsulation.

BEM

BEM (Block, Element, Modifier), is a front-end methodology developed at Yandex. BEM is actually a very complete methodology, and I honestly haven’t dug into all the details, but what I’m concerned with is simply the naming convention.

I’m using BEM-like naming conventions. The concept is the same, but the exact syntax may differ slightly.

BEM places classes into three groups:

  1. Block: the root or base of a component
  2. Element: a component inside of a Block
  3. Modifier: a variation or extension of the Block

A very basic analogy (not an example):

.dog {}
.dog__tail {}
.dog--small {}

Elements are delimited with two underscores (__), and modifiers are delimited with two hyphens (–).

In the above analogy, we see that .dog is the Block, the root of element. Then, .dog__tail is an Element, it is a smaller part of a .dog Block. Lastly, .dog--small is Modifier, a specific variation of the .dog Block. You can also apply Modifiers to Elements. for example, we could have .dog__tail--short to again, specify a variation on the dog__tail Element.

In some cases I may want multiple words for Blocks, Elements or Modifiers. In any case, these are separated with a single hyphen (-), and classes are always written in lowercase.

Preprocessors

I’ve been spending time working CSS Preprocessors into my work flow, and so far, it’s been incredibly valuable. CSS Preprocessors take code that is written in a preprocessed language and convert them to good old CSS. They are not CSS, which means they are not bound be the same rules and limitations of CSS. While CSS is great, it doesn’t always allow us to easily do the things we’d like to do.

For example, one thing that would be really nice in CSS is variables. Maybe you want something to have the left margin of one element the same as the width of another, and suddenly someone decides that those numbers need to change. Since they’re the same number, and your layout might rely on that number, you have to change it more than one place. But with a varibale you could change it in just one place and have it reflect in the whole layout. Of course, there is a lot more to preprocessors than just variables, but that’s a start!

You obviously don’t have to use a preprocessor, but I think you’ll find most people who do, won’t go back. I know I won’t. The gain in flexibility, and increased readability are something I just can’t give up. Simply being able to use variables and mixins is enough to keep me hooked.

There are several preprocessors available, but the only two I’ve really looked at and used at all are LESS and SASS. Please take a look, and consider adding one of these to your workflow, you won’t look back.

Concluding

My real point here, is that CSS can be better. Everything can be better. Someone told me recently in a comment on a post on Reddit that “CSS doesn’t have semantics”. I wholeheartedly disagree. CSS 100%, without a doubt can be semantic.

Using OOCSS and BEM does, in fact, give your CSS a very semantic meaning. This doesn’t mean it’s easy right off the bat, but it’s well worth exploring. Combine that with CSS Preprocessors, and you have the potential for very readable, maintainable, and scalable CSS.

I’d also like to note that this not only makes your CSS (preprocessed or not) more readable, but also makes your HTML more readable, by applying semantic class names to elements.

TL;DR

Ok, maybe that was a lot – to summarize, write better CSS by doing this:

Object Oriented CSS:

  • each class does one thing — it does it well, it does it right

Block, Element, Modifier (BEM) style class names:

  • Block: .grid
  • Element: .grid__item (2 underscores)
  • Modifier: .grid--wide (2 hyphens)

Preprocessors are awesome:

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Mark Rabey

Hi, my name is Mark. I am a full-stack web developer who’s passionate about user experience. I believe in creating scalable systems, and therefore I focus on writing clean, clear, maintainable code for websites and web applications. I write, work and teach about web design and development. You can follow my work on Twitter, Facebook, GitHub or on my site.

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