The last two posts of this series on CSS Flexbox focused on all the properties of flexbox applied to flex-container and flex-items.

In this post, we will go through some of the popular and common use cases of CSS flexbox.

This post is quite long as I have explained all the use cases in detail.

At the end of this blog post, I will also share some useful resources to learn CSS Flexbox in the easiest possible way!

COMMON USE CASES OF CSS FLEXBOX

Aligning items with space between
Aligning items horizontally
Centering content
Splitting a container halfway

We will use the example in the images below and try to see how flexbox was used create this webpage.

Find the template code for the website here

1. ALIGNING ITEMS WITH SPACE BETWEEN

One use of flexbox is to align elements with space between them.

In the example website, navbar in the header has 2 sections: logo and the navigation links.
They are placed such that there is space between them, and are pushed to either side of the navbar.
Using the template code below for the navbar, let's see how the logo and navbar can be pushed with space between them.

To convert this into a proper navbar, we need to focus on the parent of both <h1> and <nav>: the div with navbar class.

  .navbar {
      display: flex;
      justify-content: space-between;
      align-items: center;
  }

That's all! 3 lines of code and then logo and navigation links are pushed to either sides with space between.

display: flex converts the navbar container into a flex-container.
- The <h1> and <nav> are placed horizontally. flex-direction: row; is the default main-axis.
- justify-content: space-between; separates the flex-items with space between them and pushes them to opposite sides of the container (main-start and main-end).
- align-items: center; places the flex-items in the vertical center of the flex-container.
  - NOTE: When justify-content: space-between; is used on a container with more than 2 flex-items, then they are spread out within the container, with 1^st item near the main-start and last item pushed to main-end.
  - This can be used in the situation when header only has navlinks.
- Go through this post to learn about justify-content

Check out the GIF below to understand how the above code works.

This is the final look of the navbar with space between the logo and navlinks.

2. ALIGNING ITEMS HORIZONTALLY

Another common use case of flexbox is to align items horizontally within a container

In the example website, the navlinks have been placed horizontally within the navbar.
In the example use case 1 above, logo and the navlinks have been placed properly, but the navlinks are still displayed vertically.
Using the code below as template, let's see how the navigation links can be aligned horizontally.
To align all the navlinks horizontally, we need to focus on the <ul> and <li> within .navbar nav.
```
  .navbar nav ul {
      display: flex;
  }
```

display: flex makes sure the <ul> becomes a flex-container, and by default all the children, <li> are horizontally aligned.

Check out the GIF below to understand how this works.

This is the final look of the navlinks within the navbar.

3. CENTERING CONTENT

This is probably the most common use case of flexbox: to center content vertically and horizontally.

In the example webpage above, notice how text within the showcase image is centered vertically as well as horizontally.
Using the below starter code, let's see how text (or any other content!) can be centered within a container.
We need to grab the parent container of the content that needs to be centered.

In this case, parent element of <h1>, <p> and <a> is the div with id showcase-content.

  #showcase-container {
      display: flex;
      flex-direction: column;
      justify-content: center;
      align-items: center;
  }

Here the main-axis is column, so applying flex to the #showcase-container stacks <h1>, <p> and <a> vertically.
- justify-content: center; centers content along the main-axis: column.
- align-items: center; aligns content to the center along the cross-axis: row.
  - Using these together centers content vertically and horizontally.
- NOTE: You can play around with combinations of justify-content and align-items to test various alignment of elements within the parent container.
- Check out this post to learn more about justify-content and align-items

Check out the GIF below to understand how centering content works.

This is the final look of the showcase and text within.

4. SPLITTING A CONTAINER HALFWAY

The main agenda behind flexbox is that it easily aligns elements even if the initial size is unknown or dynamic.

In the example webpage above, the cards in the main section are split such that one half has an image and the other half content.
Using the below starter code, let's see how we can into two equal sections.
As usual let's grab the parent container of the container that needs to be split.

The parent of <img> and <h3>, <p> container with class card-body-column, which is the div with class card-body.

  .card-body {
      display: flex;
      flex-wrap: wrap;
      justify-content: center;
  }

The above code makes both the div with class card-body-column flex-items.
- Although these 2 items are supposed to be aligned horizontally they are wrapped onto different lines since their initial width overflows the container. This behavior is due to flex-wrap: wrap;

Let's now focus on aligning the items horizontally for which we need to grab the container with class card-body-column.

  .card-body .card-body-column {
      flex: 1;
  }
  .card-body img {
      height: 100%;
      width: 100%;
      object-fit: cover;
  }

Adding flex: 1; to .card-body-column makes the container grow or shrink from same initial width: 0. Hence, now we obtain 2 equal containers that grows equally.
- But the image does not occupy the entire part of the container, hence we set the width and height to 100%.
- To ensure that width to height ratio is not distorted as the container shrinks or grows we also add object-fit: cover;. This places the image as a cover in it's part of the container.
- NOTE: We can split the containers into sections of different ratios by increasing the value of flex for one half of the container.

Check out the GIF below to understand how splitting of content works.

Check out the GIF below how object-fit: cover; helps the image.

This is the final look of the showcase and text within.

FLEXBOX AND MEDIA QUERIES

A good website is one that works seamlessly on all devices of all sizes.
Although flexbox makes layouts easy, we need to add responsiveness. This can be done using media queries.
Let's look at the image within the card container mentioned above in use case 4.
Notice how this image shrinks in screens of small sizes. This obviously isn't very appealing. So let's tackle this issue.
Let's set a max width and ensure that once the screen width becomes smaller than the max-width, we will change the flex-direction to column.
This way when the screen size becomes too small, the card content will be stacked on top of each other hence avoids shrinking.

@media (max-width:540px) {
    .card-body {
         flex-direction: column;
    }
}

As the screen size becomes less than 541px, the main-axis becomes column. Otherwise, it's the default row.

The same responsiveness can be applied to the logo and navlinks to be stacked vertically and in the center the navbar.

Using just 4 common use cases, we managed to build a small webpage! Find the completed website code here

There are so many more use of flexbox out there which you can easily discover by tinkering with flexbox properties and creating websites.

As as a side note, different developers use varying combinations of flex properties to bring out the same effect.
- For e.g. to separate the logo and navlinks, you may see that justify-content: space-between may not be used, but rather align-self is used on the individual flex-items.
Another major takeaway is that flexbox is not the end of responsive design, and this may not be the easiest solution for certain situations.
- For e.g., say you want to split your website into header, main, sidebar and footer. In such cases, CSS GRID is much more simpler and faster.

THERE IS NO SINGLE RIGHT WAY TO DO THINGS! YOU ADAPT AND LEARN AS YOU EXPLORE!

RESOURCES

As promised, I'll drop a few resources that helped me in learning CSS Flexbox easily and efficiently. Hope this helps you.

CSS MDN Web Docs: Take your time to read through the docs as the explanations are highly detailed and precise.
CSS Tricks: Another gem of a resource where basics for flexbox are explained as well.
W3C Flexbox Docs: A very detailed and in-depth understanding to CSS Flexbox
W3Schools: Another resource having short explanations with good examples

These aren't enough as once you grasp the theory, you will have to apply them somewhere.

Below are some fascinating games and challenges which will help you understand flexbox practically AND visually!

Flexbox Defense
- A wonderful fantasy game where you use flex properties to stop enemies from getting into your defenses.
Flexbox Froggy
- Another game where flex properties are used to help froggy and friends to guide them to their lillipads!
Flexbox Code Generator
- This site allows you to visualize flex properties, and play around by changing combination of properties
Building UI with CSS Flex
- This site has challenges for you to build neat, and awesome UIs with the help of CSS Flexbox.
Dev Challenges
- Another website that has front-end and responsive web developer challenges to build components and sites!

And that's a (flex) wrap on the CSS Flexbox series.

Thank you so much for going through the blog post and sticking till the end.
Please do leave a like and share it with your dev friends!

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Common Use Cases of CSS Flexbox

Bharati Subramanian