SVG is great. Best way to build scalable graphics on the web. SVG can do everything from simple logos to data visualization and even animation.

The best part is, you can manipulate SVG with both CSS and JavaScript. It’s an image that’s part of your DOM. 🀯

Look at this animated fire example. Isn’t it neat? No animated image required, just some SVG elements and a bit of JavaScript.

No wonder then that SVG is the norm when it comes to data visualization and other programmable graphics.

Just one problem: SVG sucks at layout

Absolutely terrible. There’s no layout support at all. You get absolute positioning and that’s it. Sure, you can position absolutely within absolutely positioned elements, which is sort of relative positioning, but ugh …

Absolute positioning hell

A React + D3 dashboard of scatterplots

A React + D3 dashboard of scatterplots

Say you’re building a small dashboard. Like of different scatterplots looking at a dataset about dog breeds.

Because the data is there, and you can, of course.

You create a scatterplot component. It takes an x and a y position and sizing info. Inside, it places two axes, a caption, and the datapoints.

The <Scatterplot> is absolutely positioned via a translate transformation. That moves an SVG element by a vector from (0, 0), thus rendering at the (x, y) coordinate.

You render each scatterplot like this:

<Scatterplot
        data={data}
        x={100}
        y={100}
        width={350}
        height={350}
        filter={d =>
            d.weight &&
            d.height &&
            d.weight[0] &&
            d.height[0]
        }
        xData={d => d.weight[0]}
        yData={d => d.height[0]}
        xLabel="Weight (lbs)"
        yLabel="Height (in)"
        title="Dog Breed Height & Weight"
        entry={props => (
            <Datapoint
                breed={props.d.breed}
                {...props}
            />
        )}
    />

A lot of arguments, I know. Data, positioning, sizing, functions for interpreting data, a few labels, and a render prop for each datapoint.

Once positioned with a grouping element <g>, the scatterplot can use quasi-relative positioning for its elements.

render() {
    return (
        <g transform={`translate(${x}, ${y})`}>
            <Heading y={-25}>{title}</Heading>
            {data.map(d =>
                entry({
                    x: xScale(xData(d)),
                    y: yScale(yData(d)),
                    d: d
                })
            )}
            <Axis
                scale={xScale}
                x={0}
                y={height}
                type="Bottom"
                label={xLabel}
            />
            <Axis scale={yScale} x={0} y={0} type="Left" label={yLabel} />
        </g>
    );
}

Position the main container at x and y. Place Heading at (0, -25), datapoints at wherever they go, one axis at (0, 0), and another at left bottom. All relative to the parent container.

The parent container is technically relative to the whole SVG container … πŸ€”

Absolute or relative, doesn’t matter. You’re gonna have one hell of a fun time calculating the position of each individual element by hand. D3 scales help, but you still have to think about it.

SVG itself offers zero help.

Want to resize your scatterplots? Here’s what happens πŸ‘‡

Smaller scatterplots, gotta update positions

Smaller scatterplots, gotta update positions

Want to resize your browser? Here’s what happens πŸ‘‡

Resized browser cuts off visualization

Resized browser cuts off visualization

Ugh.

react-svg-flexbox to the rescue

You can fix the layouting problem with react-svg-flexbox. It’s a small library, not a lot of stars, but omg so perfect.

Built on top of Facebook’s css-layout, which has recently become a part of yoga, it lets you use CSS flexbox to position SVG elements.

Flexbox might be confusing to grok – I look at tutorials any time I use it for anything – but it’s way better than doing it yourself. How many engineers worked on browser layout engines over the past two decades?

Wouldn’t wanna retrace all those steps yourself πŸ˜…

Wrap our dashboard in a <Flexbox> element and…

import Flexbox from "react-svg-flexbox";
 
// ...
 
// render() etc.
<Svg>
    <Flexbox
        style={{
            flexDirection: "row",
            justifyContent: "flex-start"
        }}
    >
        <Scatterplot
            data={data}
            width={200}
            height={200}
            filter={d =>
                d.weight &&
                d.height &&
                d.weight[0] &&
                d.height[0]
            }
            xData={d => d.weight[0]}
            yData={d => d.height[0]}
            xLabel="Weight (lbs)"
            yLabel="Height (in)"
            title="Dog Breed Height & Weight"
            entry={props => (
                <Datapoint
                    breed={props.d.breed}
                    {...props}
                />
            )}
        />

We take <Flexbox> out of react-svg-flexbox, use flexbox styles to say we want to render in a row that starts at the beginning, and the rest happens on its own.

Note that react-svg-flexbox passes x and y props into our components, so we had to take out manual positioning. Our dashboard now uses up all the space it can πŸ‘‡

Scatterplots rendered in a flexbox row

Scatterplots rendered in a flexbox row

Something’s funky with our vertical positioning, but it’s an easy fix. Offset y coordinates by a few pixels. Β―_(ツ)_/Β― it’s not happening in the official examples, so it must be something we’re doing inside those scatterplots.

The axes are still poking outside our width bounds, but this looks better already.

Scatterplots with a vertical offset

Scatterplots with a vertical offset

Even if we make one of them bigger, everything still works. No changes to positioning required! o/

One big scatterplot

One big scatterplot

Responsive layout with react-svg-flexbox

For the biggest win, we add flexWrap: wrap to our <Flexbox> component. Like this πŸ‘‡

 <Flexbox
    style={{
        flexDirection: "row",
        justifyContent: "flex-start",
        flexWrap: "wrap",
        width: 1024,
        height: 1024
    }}
>

You have to specify available width in your styles, otherwise, it doesn’t work. That means you should listen to window.onresize and update width accordingly.

Easiest to attach an event listener in componentDidMount. Like this:

class App extends Component {
    state = {
        width: 1024
    };
 
    svgRef = React.createRef();
 
    componentDidMount() {
        window.addEventListener("resize", this.updateSize);
    }
 
    componentWillUnmount() {
        window.removeEventListener("resize", this.updateSize);
    }
 
    updateSize = () => {
        this.setState({ width: this.svgRef.current.clientWidth });
    };
 
    render() {
        // ...
 
        <svg
            style={{ width: "100%", height: 1024 }}
            ref={this.svgRef}
        >
            <Flexbox
                style={{
                    flexDirection: "row",
                    justifyContent: "flex-start",
                    flexWrap: "wrap",
                    width: this.state.width,
                    height: 1024
                }}
            >
    }

And your dashboard becomes responsive! Yay

See the code, play with examples

You can see a full set of react-svg-flexbox examples on their Storybook.

Code for my dog breed dashboard example is on GitHub here.

You can try it live here.

Fin

Use react-svg-flexbox. Your life will improve. The best thing that’s ever happened to me for SVG coding.

Thanks Cody Averett for finding this gem πŸ’Ž

Learned something new? Want to improve your skills?

Join over 10,000 engineers just like you already improving their skills!

Here's how it works πŸ‘‡

Leave your email and I'll send you an Interactive Modern JavaScript Cheatsheet πŸ“–right away. After that you'll get thoughtfully written emails every week about React, JavaScript, and your career. Lessons learned over my 20 years in the industry working with companies ranging from tiny startups to Fortune5 behemoths.

PS: You should also follow me on twitter πŸ‘‰ here.
It's where I go to shoot the shit about programming.