CSS pseudo-elements: `before` and `after`

CSS pseudo-elements: `before` and `after`

My first job was at a firm that created custom websites. They mostly looked awesome and were CSS-heavy. I was an hour into my first day when I already encountered a ::before - something a junior rarely uses at home when learning and it's hard to grip at if no one explains it to you.

Few weeks passed with copy-pasting the ::before CSS from other projects, but then I got it and it wasn't that difficult to use. But copy-pasting something you don't understand is never a good idea. That's why I gathered most of the information about ::before and ::after in this blog. So you won't be in a position of copy-pasting without understanding as I was doing it and because ::before is pretty awesome when you got to know it. There are endless possibilities for creation with it when you're comfortable using it.

main.PNG

What will I learn

At first, we will review the pseudo-elements, the difference between before and after. The main property of a before/after selector is a content. There are many possibilities for its value and in the second part of this blog, we will review some of them:

  1. a string
  2. an attribute
  3. an image
  4. nothing

For each value, I provided at least one showcase that should give you a fair picture of what's going on.

This is not a tutorial, showcases are not explained in depth. I suggest you copy-paste (or, even better, retype) each of the showcases and play with it a little, it will help you to understand those two pseudo-elements better.

Prerequisites

  1. Basic knowledge of HTML
  2. Basic knowledge of CSS

Pseudo-elements

Pseudo-element is an element that doesn't exist in the document tree but appears on the page as it would. To simplify - pseudo-element (like ::before) is a 'faker' that pretends to be there, but it isn't.

::before and ::after leaves your markup semantic, but at the same time they give you a lot of extra design possibilities. Think of them as two extra tickets to add cosmetic content to an element.

Besides ::before and ::after, other pseudo-elements are: ::first-letter, ::first-line and ::selection. They behave a little differently though because you aren't creating new content. Rather, you're selecting only a part of a tag, it's like creating a non-existing span.

You might expect them to be before or after the element, but that's not the case. Pseudo-element is the first child of the selected element. That means they appear inside the element, next to its content.

They have few negative sides though:

  • you can’t attach an event only to a pseudo-element
  • most screen readers read the content of a pseudo-element (here is a solution for that, but it doesn't work on most browsers)
  • you usually can't select it

You can't create ::before or ::after on the self-closing tags. So <img />, <input /> or <hr /> can't have ::before!

Here's how that looks in practice:

HTML

<div class="myelement">
    Text in "myelement".
</div>

CSS

.myelement {
    color: red;
}
.myelement::before {
    content: "I'm before";
}

Browser

browser.PNG

Page source

before.PNG

As you see, both texts are visible in the browser. But the ::before text isn't visible in the page source. Also, we set the color to red on .myelement and ::before inherited it.

::before or ::after?

::before and ::after behave very similar. The only difference is how they position themselves in the browser and the page source.

Page source ::before appears before the content of the child and ::after appears after it. They are both inside the element.

beforeaftersource.PNG

Browser

If we don't manipulate their position, naturally ::before comes before the element's content and ::after comes after it.

beforeafterbrowser.PNG

You can choose between those two based on where are you trying to put the additional element, but it's not necessary.

FontAwesome icon ::before the element

beforeicon.PNG

FontAwesome icon ::after the element

aftericon.PNG

Since ::before and ::after are pretty much the same, I'm going to use only the ::before for the rest of the tutorial. Whatever I write for the ::before goes the same for the ::after too!

Stacked

However, if ::before and ::after are stacked on top of each other, the ::after will be positioned on the top of before. If we create two squares of different colors and sizes and position them on top of each other, the ::after square (blue) will cover part of the ::before square (orange). That's because the after is later in source-order.

CSS

               .myelement::before {
                   content: "";
                   width: 50px;
                   height: 50px;
                   background-color: orange;
                   position: absolute;
                   left: 0;
               }

               .myelement::after {
                   content: "";
                   width: 30px;
                   height: 30px;
                   background-color: blue;
                   position: absolute;
                   left: 0;
               }

Browser

sameposition.PNG

As you can see, the orange ::before square is partly covered by the blue ::after square.

For now, don't fuss if you don't know what is going on, we'll cover that later on. This is just to show you the difference between ::before and ::after

:before or ::before?

At first, there was :before. Later, they distinguished between pseudo elements and pseudo selectors (eg. `:first-child).

  • pseudo-elements have double-colon selectors(::)
  • pseudo-selectors have single-colon selectors (:)

before is a pseudo-element, so you should use :: if you want to do it right.

BUT - enters Internet Explorer. Internet Explorer 8 and below only supports :

All modern browsers support it both ways, so if you need to support old IE or you're just used to it, you can use :before, no fuss.

Possible values for content

The most important part of ::before is the content. Content can be a lot of things:

  1. a string
  2. an attribute
  3. an image
  4. nothing
  5. open-quote and close-quote
  6. no-open-quote | no-close-quote
  7. counter()
  8. alternative text

Here I'll showcase the ones I think are the most useful.

String

That one is pretty straightforward. You can use a string and it can contain unicode special characters.

Special characters need to be specially encoded as a unicode entity. Check the ASCII code for the chosen character here and convert it to CSS value here: evotech.net/articles/testjsentities.html

Showcase: Comment

Add a string 'Comment' before each comment on a blog.

<div class="comment">
    That post is great!
</div>
        .comment::before {
            content: "Comment: ";
        }

Comment.PNG

Add a copyright special character before an author of a page.

<div class="copyright">
    GirlThatLovesToCode
</div>
     .copyright::before {
            content: "\00A9";
     }

copyright.PNG

Attribute

You have access to the parent element's (the one you're creating ::before on) attributes and can use them as the content for the ::before.

Here is the list of all possible attributes.

<a href="https://girlthatlovestocode.com/" id="linkOnHover">Check this awesome link</a>
#linkOnHover:hover::after {
    content: ": " attr(href);
}

hoverHref.PNG

As you can see, you can bind ::after just on :hover too!

Image

You can show an image in your ::before. This is so useful for styling (eg. lists)! Because gradients are essentially images, the same rule applies to them.

The image is inserted at its exact dimensions and can't be resized.

Showcase: Ducky

<p class="rubber-duck">
    In software engineering, <span>rubber duck</span> debugging is a method of debugging code. The name is a reference to a story in the book The Pragmatic Programmer in which a programmer would carry around a <span>rubber duck</span> and debug their code by forcing themselves to explain it, line-by-line, to the <span>duck</span>.
</p>
.rubber-duck span::after {
    content: url("duck.png");
}

duckie.PNG

Showcase: Gradient

<p class="gradiented">
    You can even use gradient as an image!
    Nullam in enim id leo mollis dapibus. Ut eget arcu nunc. Proin in purus accumsan, elementum felis ut, mollis tellus.
[... There is more text on the image]
</p>
.gradiented {
    position: relative;
    width: 500px;
}

.gradiented::before {
    content: linear-gradient(to bottom, red, yellow);
    position: absolute;
    width: 100%;
    height: 100%;
    z-index: -1;
}

gradient.PNG

Here is a little more going on than on the rest of the showcases. Position, width, and height on ::before are all needed for the gradient to be visible. If you drop any of those, the gradient won't be visible. We added a z-index so the gradient doesn't cover the text. It's sent to the background instead. Because absolute positioned element is positioned regarding the first positioned element, we had to set the position for its parent element.

Nothing

You might want to create something with CSS, not just set your content to something (eg. image in the background, so you can resize it). In that case, you can't just exclude content - there is no ::before without content. You will want to set the content to an empty string.

Comment out the properties that you're not sure why they are here. You'll see what changes.

Showcase: Image as a background

<div class="img-bg">
    I want to have an image on the left side of the text. But my image is too big and I can't resize it if I put it in the content.
</div>
.img-bg {
    position: relative;
    margin: 300px;
    width: 400px;
}

.img-bg::before {
    content: "";
    background-image: url(circle-cropped.png);
    position: absolute;
    width: 100px;
    height: 100px;
    background-size: cover;
    left: -120px;
    top: -30px;
}

bgImage.PNG

We've set the div's width and height, so it looks better. As in some cases before, it's position is set to relative so we can position the ::before absolutely. If the content is empty, you need to set position as absolute if you want the background to be visible. When working with background, you have to set width, height, and background-size for the background to be visible. left and top just covers the cosmetics - so the image is where it should be.

Showcase: Speech buble

<div class="speech">My name is GirlThatLovesToCode. That's becouse I'm a girl and I love to code.</div>
.speech{
    position: relative;
    padding: 30px;
    max-width: 500px;
    background: #add8e6;
    margin: auto;
}

.speech::after {
    content: "";
    position: absolute;
    top: 20px;
    left: -30px;
    width: 0;
    border-width: 30px 30px 0;
    border-style: solid;
    border-color: #add8e6 transparent;
}

speech.PNG

I won't explain the creating of a speech bubble here as that could be a whole new tutorial. Just notice the positions that are set and that ::after has no content. The only thing that exists in there, is a border that is shaped into a triangle.

Here you can create your speech bubbles and play with it.

Extra: Combine the before and after

Once you're familiar with the possibilities that ::before and ::after offers you, you can combine them.

If you just add the previously created class img-bg you created before, to the div with class speech, like this:

<div class="speech img-bg">My name is GirlThatLovesToCode. That's because I'm a girl and I love to code.</div>

and you make no change to the existing CSS, this is what you get:

speechandimgbg.PNG

Conclusion

Now you should have a better understanding of pseudo-elements ::before and ::after. They are a great way to upgrade your styling, but should never be used for the actual content of your webpage. The most important part of ::before is content. Depending on what you're trying to achieve, you select one of the possible values for content. You can style your ::before with the same CSS rules as you would style any other element. Keep in mind that the showcases were just examples, used to show the ideas, how you use ::before is dependant on your design.

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