In React, you sometimes need to allow users to pass in a tag name prop to a component as a string. You may have encountered this pattern if you’ve ever worked with the react-intl library for internationalized strings, where the FormattedMessage component accepts an optional tagName prop:

<FormattedMessage id="common.close" tagName="p" />

Layout components are a good real-world use case for this—they might apply some styling under the hood, but they should still be flexible enough to render any valid HTML tag. Examples include reusable grid layouts (which need not always render divs), vertical rhythm layouts, and more.

To keep this tutorial simple, I’ll create a pointless demo component:

import { FC } from 'react';
interface ComponentProps {}
const Component: FC<ComponentProps> = (props) => <div {...props} />;

You could always render a div, but that’s inflexible—it may work well for most use cases, but there could also be situations where you need to render a different tag for semantics.

To fix this, you can use the ElementType type to allow passing in a tag name as a prop:

import { ElementType, HTMLAttributes, FC } from 'react';

interface ComponentProps extends HTMLAttributes<HTMLOrSVGElement> {
  as?: ElementType;
}

const Component: FC<ComponentProps> = ({ as: Tag = 'div', ...otherProps }) => {
  return <Tag {...otherProps} />;
};

export default Component;

There are two things worth noting here.

First, React expects component names to be capitalized; lowercase names are reserved for built-in tags. But we want to follow the convention of using lowercase names for the tag name prop. To get around this, we destructure the as prop and alias it as Tag.

Second, our component renders a div by default. We do this with destructuring and default assignment in the component’s signature. But you can override this behavior by passing in a custom tag name on an as-needed basis:

import Component from 'components/Component';
import { FC } from 'react';

const Parent: () => {
  return <Component as="p" />
};

Since we’ve specified that the as prop is of type ElementType, we’ll get auto-complete intellisense whenever we try to set this prop:

An example of using the Component component and passing in a concrete tagName. VS Code's intellisense shows an auto-complete dropdown for you as you type.

In some cases, you may want to instead use render props, but they’re not always needed—sometimes, all you really want is to be able to specify a tag name as a string. You typically only need to use render props if the element needs to know about the component-level state to decide how to render itself. Here, we’re just telling the component what to render by passing in a plain string as a tag name prop. The syntax is shorter and easier to read.

And that’s all there is to it!

Attributions

Social media preview: Photo by Angèle Kamp (Unsplash).

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