javascript - How to dynamically import SVG and render it inline

Question

I have a function that takes some arguments and renders an SVG. I want to dynamically import that svg based on the name passed to the function. It looks like this:

import React from 'react';

export default async ({name, size = 16, color = '#000'}) => {
  const Icon = await import(/* webpackMode: "eager" */ `./icons/${name}.svg`);
  return <Icon width={size} height={size} fill={color} />;
};

According to the webpack documentation for dynamic imports and the magic comment "eager":

"Generates no extra chunk. All modules are included in the current chunk and no additional network requests are made. A Promise is still returned but is already resolved. In contrast to a static import, the module isn't executed until the call to import() is made."

This is what my Icon is resolved to:

> Module
default: "static/media/antenna.11b95602.svg"
__esModule: true
Symbol(Symbol.toStringTag): "Module"

Trying to render it the way my function is trying to gives me this error:

Objects are not valid as a React child (found: [object Promise]). If you meant to render a collection of children, use an array instead.

I don't understand how to use this imported Module to render it as a component, or is it even possible this way?

Answer 1

You can make use of ref and ReactComponent named export when importing SVG file. Note that it has to be ref in order for it to work.

The following examples make use of React hooks which require version v16.8 and above.

Sample Dynamic SVG Import hook:

function useDynamicSVGImport(name, options = {}) {
  const ImportedIconRef = useRef();
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState();

  const { onCompleted, onError } = options;
  useEffect(() => {
    setLoading(true);
    const importIcon = async () => {
      try {
        ImportedIconRef.current = (
          await import(`./${name}.svg`)
        ).ReactComponent;
        if (onCompleted) {
          onCompleted(name, ImportedIconRef.current);
        }
      } catch (err) {
        if (onError) {
          onError(err);
        }
        setError(err);
      } finally {
        setLoading(false);
      }
    };
    importIcon();
  }, [name, onCompleted, onError]);

  return { error, loading, SvgIcon: ImportedIconRef.current };
}

Sample Dynamic SVG Import hook in typescript:

interface UseDynamicSVGImportOptions {
  onCompleted?: (
    name: string,
    SvgIcon: React.FC<React.SVGProps<SVGSVGElement>> | undefined
  ) => void;
  onError?: (err: Error) => void;
}

function useDynamicSVGImport(
  name: string,
  options: UseDynamicSVGImportOptions = {}
) {
  const ImportedIconRef = useRef<React.FC<React.SVGProps<SVGSVGElement>>>();
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState<Error>();

  const { onCompleted, onError } = options;
  useEffect(() => {
    setLoading(true);
    const importIcon = async (): Promise<void> => {
      try {
        ImportedIconRef.current = (
          await import(`./${name}.svg`)
        ).ReactComponent;
        onCompleted?.(name, ImportedIconRef.current);
      } catch (err) {
        onError?.(err);
        setError(err);
      } finally {
        setLoading(false);
      }
    };
    importIcon();
  }, [name, onCompleted, onError]);

  return { error, loading, SvgIcon: ImportedIconRef.current };
}

---

For those who are getting undefined for ReactComponent when the SVG is dynamically imported, it is due to a bug where the Webpack plugin that adds the ReactComponent to each SVG that is imported somehow does not trigger on dynamic imports.

Based on this solution, we can temporary resolve it by enforcing the same loader on your dynamic SVG import.

The only difference is that the ReactComponent is now the default output.

ImportedIconRef.current = (await import(`!!@svgr/webpack?-svgo,+titleProp,+ref!./${name}.svg`)).default;

---

Also note that there’s limitation when using dynamic imports with variable parts. This SO answer explained the issue in detail.

To workaround with this, you can make the dynamic import path to be more explicit.

E.g, Instead of

// App.js
<Icon path="../../icons/icon.svg" />

// Icon.jsx
...
import(path);
...

You can change it to

// App.js
<Icon name="icon" />

// Icon.jsx
...
import(`../../icons/${name}.svg`);
...