Pure CSS Bar Graphs with Graceful Mobile Fallbacks

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I recently published a new open source project, Flexbox Bar Graphs, and wanted to share a simple breakdown of how it was built. It isn’t anything mind-blowing, but I like the idea of placing bar graphs in a web page with zero Javascript.

So in the end, this is what our bar graphs will look like on desktop:

Flexbox Bar Graph
The flexbox bar graph in desktop view (direct link to image)

And this is how it will look on smaller devices:

Flexbox Bar Graph Table
The flexbox bar graph on mobile devices (direct link to image)

Let’s get into the details!

The HTML

The main “secret” of this project is that our graphs are constructed out of HTML tables. Now before you freak out - this is perfectly fine and works in our favor quite well.

  1. If the user has JS disabled –> they will still see our graphs
  2. If the user has CSS disabled –> they will see a standard data table set

All bases are covered!

<!-- Using a basic table with our custom data-id -->
<table data-id="flexbox-bar-graph">
    <caption>Web Performance Results</caption>
    <thead>
        <tr>
            <th>Test Performed</th>
            <th>Before</th>
            <th>After</th>
            <th>Difference</th>
        </tr>
    </thead>
    <tbody>
        <tr>
            <th>Initial Load Time</th>
            <td>
                <!--
                    WTF are these CSS variables?
                    See the CSS section below
                -->
                <span style="--data-set:4.7/5;"></span>
                <p>4.7</p>
            </td>
            <td>
                <span style="--data-set:2.7/5;"></span>
                <p>2.7</p>
            </td>
            <td>
                <span style="--data-set:2/5;"></span>
                <p>2</p>
            </td>
        </tr>
    </tbody>
</table>

Nothing crazy is happening here - just your standard HTML table structure. The one main thing to notice is the --data-set CSS variable placed inline on each data point. This will be important for our CSS to configure the individual bar graphs properly.

The CSS

This might look overwhelming if I just dumped the whole CSS file in one big code block, so instead I’m going to break them down into two parts:

  1. Baseline styling (mobile)
  2. Desktop styling

Baseline

Here we target just our table elements with the data-id of flexbox-bar-graph. This allows us to avoid worrying about adding classes or IDs and also avoids conflicts with other non-graph styled tables in our projects.

The base :root element holds all of our bar graph colors. Change these as you see fit!

/* Bar Graph color variables */
:root {
    --bar-color-1: #357EC7;
    --bar-color-2: #E42217;
    --bar-color-3: #4CC417;
    --bar-color-4: #7D0541;
    --bar-color-5: #FFD801;
}

[data-id="flexbox-bar-graph"] {
    border-collapse: collapse;
    margin: 4rem 0 6rem;
    width: 100%;
}
[data-id="flexbox-bar-graph"] caption {
    text-align: left;
}
[data-id="flexbox-bar-graph"] thead th {
    text-align: right;
}
[data-id="flexbox-bar-graph"] thead th:nth-child(1),
[data-id="flexbox-bar-graph"] tbody th {
    text-align: left;
}
[data-id="flexbox-bar-graph"] tbody th {
    font-weight: normal;
    font-style: italic;
}
[data-id="flexbox-bar-graph"] tbody td {
    text-align: right;
}
[data-id="flexbox-bar-graph"] tbody td p {
    margin: 0;
}

Desktop

Now we set your “visual” bar graphs to show at a set width (in this example it is 1000px and above). That way the “default” styling can target the mobile device screen sizes.

@media(min-width: 1000px) {
    [data-id="flexbox-bar-graph"] {
        background: transparent;
        display: block;
        min-height: 400px;
        padding: 0;
        position: relative;
        width: 100%;
    }

    [data-id="flexbox-bar-graph"] caption {
        display: block;
        font-size: 2rem;
        text-align: center;
        width: 100%;
    }

    [data-id="flexbox-bar-graph"] thead {
        display: block;
        margin: 2rem 0 3rem;
        width: 100%;
    }
    [data-id="flexbox-bar-graph"] thead tr {
        border-bottom: 1px solid lightgrey;
        display: flex;
        justify-content: center;
        padding-bottom: 1rem;
    }

    [data-id="flexbox-bar-graph"] thead tr th {
        display: inline-block;
        margin: 0;
        padding: 0;
        position: relative;
        text-align: right;
    }
    [data-id="flexbox-bar-graph"] thead tr th:before {
        content:'';
        display: inline-block;
        height: 10px;
        margin: 0 0.5rem 0 2rem;
        position: relative;
        width: 10px;
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(1),
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(1):before {
        display: none;
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(2):before {
        background: var(--bar-color-1);
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(3):before {
        background: var(--bar-color-2);
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(4):before {
        background: var(--bar-color-3);
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(5):before {
        background: var(--bar-color-4);
    }
    [data-id="flexbox-bar-graph"] thead tr th:nth-child(6):before {
        background: var(--bar-color-5);
    }

    [data-id="flexbox-bar-graph"] tbody {
        display: flex;
        justify-content: space-between;
        min-height: 300px;
        width: 100%;
    }

    [data-id="flexbox-bar-graph"] tbody tr {
        display: flex;
        flex-direction: column-reverse;
        flex-wrap: wrap;
        justify-content: flex-end;
        padding: 0 50px;
        position: relative;
        width: 100%;
    }
    [data-id="flexbox-bar-graph"] tbody tr th {
        font-size: 90%;
        position: absolute;
        text-align: center;
        top: 100%;
        width: calc(100% - 100px);
    }
    [data-id="flexbox-bar-graph"] tbody tr td {
        align-items: center;
        display: flex;
        flex-direction: column;
        height: 95%;
        justify-content: flex-end;
    }

    [data-id="flexbox-bar-graph"] tbody tr td span {
        display: block;
        height: calc(var(--data-set) * 100%);
        width: 20px;
    }
    [data-id="flexbox-bar-graph"] tbody tr td:nth-of-type(1) span {
        background: var(--bar-color-1);
    }
    [data-id="flexbox-bar-graph"] tbody tr td:nth-of-type(2) span {
        background: var(--bar-color-2);
    }
    [data-id="flexbox-bar-graph"] tbody tr td:nth-of-type(3) span {
        background: var(--bar-color-3);
    }
    [data-id="flexbox-bar-graph"] tbody tr td:nth-of-type(4) span {
        background: var(--bar-color-4);
    }
    [data-id="flexbox-bar-graph"] tbody tr td:nth-of-type(5) span {
        background: var(--bar-color-5);
    }

    [data-id="flexbox-bar-graph"] tbody tr td p {
        font-size: 90%;
        margin: 0;
        text-align: center;
    }
}

Bonus Styling

In the Flexbox Bar Graph repo, I’ve also included the ability to display these bar graphs horizontally, like so:

Flexbox Bar Graph Horizontal
The flexbox bar graph in the horizontal layout (direct link to image)

The change in CSS is actually quite simple to pull this off - you just need to include the data-layout attribute on the table itself.

[data-layout="horizontal"] tbody {
    min-height: auto;
}

[data-layout="horizontal"] tbody tr {
    flex-direction: column;
    padding: 0 40px;
}
[data-layout="horizontal"] tbody tr th {
    width: calc(100% - 80px);
}

[data-layout="horizontal"] tbody tr th {
    text-align: left;
    top: calc(100% + 20px);
}

[data-layout="horizontal"] tbody tr td {
    flex-direction: row;
    height: auto;
    justify-content: start;
    margin: 10px 0;
}

[data-layout="horizontal"] tbody tr td span {
    height: 20px;
    width: calc(var(--data-set) * 100%);
}

[data-layout="horizontal"] tbody tr td p {
    margin-left: 10px;
}

That’s All Folks!

That just about sums things up. Feel free to check out the Github repo itself, open any issues you find or fork it for your own!