useRender

The useRender hook lets you build custom components that provide a render prop to override the default rendered element.

Examples

A render prop for a custom Text component lets consumers use it to replace the default rendered p element with a different tag or component.

'use client';
import { useRender } from '@base-ui/react/use-render';
import { mergeProps } from '@base-ui/react/merge-props';
import styles from './index.module.css';

interface TextProps extends useRender.ComponentProps<'p'> {}

function Text(props: TextProps) {
  const { render, ...otherProps } = props;

  const element = useRender({
    defaultTagName: 'p',
    render,
    props: mergeProps<'p'>({ className: styles.Text }, otherProps),
  });

  return element;
}

export default function ExampleText() {
  return (
    <div>
      <Text>Text component rendered as a paragraph tag</Text>
      <Text render={<strong />}>Text component rendered as a strong tag</Text>
    </div>
  );
}

The callback version of the render prop enables more control of how props are spread, and also passes the internal state of a component.

'use client';
import * as React from 'react';
import { useRender } from '@base-ui/react/use-render';
import { mergeProps } from '@base-ui/react/merge-props';
import styles from './index.module.css';

interface CounterState {
  odd: boolean;
}

interface CounterProps extends useRender.ComponentProps<'button', CounterState> {}

function Counter(props: CounterProps) {
  const { render, ...otherProps } = props;

  const [count, setCount] = React.useState(0);
  const odd = count % 2 === 1;
  const state = React.useMemo(() => ({ odd }), [odd]);

  const defaultProps: useRender.ElementProps<'button'> = {
    className: styles.Button,
    type: 'button',
    children: (
      <React.Fragment>
        Counter: <span className={styles.count}>{count}</span>
      </React.Fragment>
    ),
    onClick() {
      setCount((prev) => prev + 1);
    },
    'aria-label': `Count is ${count}, click to increase.`,
  };

  const element = useRender({
    defaultTagName: 'button',
    render,
    state,
    props: mergeProps<'button'>(defaultProps, otherProps),
  });

  return element;
}

export default function ExampleCounter() {
  return (
    <Counter
      render={(props, state) => (
        <button {...props}>
          {props.children}
          <span className={styles.suffix}>{state.odd ? '👎' : '👍'}</span>
        </button>
      )}
    />
  );
}

Merging props

The mergeProps function merges two or more sets of React props together. It safely merges three types of props:

1. Event handlers, so that all are invoked
2. className strings
3. style properties

mergeProps merges objects from left to right, so that subsequent objects’ properties in the arguments overwrite previous ones. Merging props is useful when creating custom components, as well as inside the callback version of the render prop for any Base UI component.

import { mergeProps } from '@base-ui/react/merge-props';
import styles from './index.module.css';

function Button() {
  return (
    <Component
      render={(props, state) => (
        <button
          {...mergeProps<'button'>(props, {
            className: styles.Button,
          })}
        />
      )}
    />
  );
}

Merging refs

When building custom components, you often need to control a ref internally while still letting external consumers pass their own—merging refs lets both parties have access to the underlying DOM element. The ref option in useRender enables this, which holds an array of refs to be merged together.

In React 19, React.forwardRef() is not needed when building primitive components, as the external ref prop is already contained inside props. Your internal ref can be passed to ref to be merged with props.ref:

function Text({ render, ...props }: TextProps) {
  const internalRef = React.useRef<HTMLElement | null>(null);

  const element = useRender({
    defaultTagName: 'p',
    ref: internalRef,
    props,
    render,
  });

  return element;
}

In older versions of React, you need to use React.forwardRef() and add the forwarded ref to the ref array along with your own internal ref.

The examples above assume React 19, and should be modified to use React.forwardRef() to support React 18 and 17.

const Text = React.forwardRef(function Text(
  { render, ...props }: TextProps,
  forwardedRef: React.ForwardedRef<HTMLElement>,
) {
  const internalRef = React.useRef<HTMLElement | null>(null);

  const element = useRender({
    defaultTagName: 'p',
    ref: [forwardedRef, internalRef],
    props,
    render,
  });

  return element;
});

TypeScript

To type props, there are two interfaces:

• useRender.ComponentProps for a component’s external (public) props. It types the render prop and HTML attributes.
• useRender.ElementProps for the element’s internal (private) props. It types HTML attributes alone.

interface ButtonProps extends useRender.ComponentProps<'button'> {}

function Button({ render, ...props }: ButtonProps) {
  const defaultProps: useRender.ElementProps<'button'> = {
    className: styles.Button,
    type: 'button',
    children: 'Click me',
  };

  const element = useRender({
    defaultTagName: 'button',
    render,
    props: mergeProps<'button'>(defaultProps, props),
  });

  return element;
}

Migrating from Radix UI

Radix UI uses an asChild prop, while Base UI uses a render prop. Learn more about how composition works in Base UI in the composition guide.

In Radix UI, the Slot component lets you implement an asChild prop.

import { Slot } from 'radix-ui';

function Button({ asChild, ...props }) {
  const Comp = asChild ? Slot.Root : 'button';
  return <Comp {...props} />;
}

// Usage
<Button asChild>
  <MyButton className="primary">Submit</MyButton>
</Button>

In Base UI, useRender lets you implement a render prop. The example below is the equivalent implementation to the Radix example above.

import { useRender } from '@base-ui/react/use-render';

function Button({ render, ...props }) {
  return useRender({
    defaultTagName: 'button',
    render,
    props,
  });
}

// Usage
<Button render={<MyButton className="primary" />}>Submit</Button>

Render prop and polymorphism

The render prop is primarily designed for composing event handlers and behavioral props. In most cases it should render the same tag as the default element.

Using render for polymorphism (rendering a different tag) requires more care, as some default props may not be valid on the new element. For example, type="button" is only valid on a <button>. Since the component can’t know what element render will produce at render time and before hydration, props like these need an explicit signal. This is why Base UI’s Button provides a nativeButton prop to control which defaults are applied.

Stencil API

import { h, useRender } from 'finesoft-components/use-render';

const element = useRender({
  defaultTagName: 'button',
  state: { active: true },
  props: { children: 'Action' },
  render: h('a', { href: '/details' }),
});

useRender returns a Stencil VNode. Call it from a Stencil component’s render() method, or mount the result with the public render(vnode, container) function. It is not a React hook. For native VNode SSR, use renderVNodeToString(vnode) from the same entry; custom-element declarations can then pass through finesoft-components/hydrate. The examples use this serializer and the same consumer render function on the server and in the browser.

Boolean true state becomes an empty attribute; falsy values are omitted. Attribute names use the lowercased state key. Explicit props override generated attributes. Default buttons use type="button", and default images use alt=""; explicit props can override these defaults.

VNode overrides merge classes, styles and handlers and retain their own children. Callback overrides receive the resolved props and state directly. Object and callback refs from props, render and ref are combined. Callback cleanup functions run on replacement or unmount; legacy callbacks receive null. Stable refs stay attached across updates.

When building your own Stencil component in another project, use a local factory backed by that project’s h. Stencil detects render capabilities from local h() calls: the dynamic props argument retains event, ref, class and style support, and the explicit SVG branch retains SVG support. Passing only an imported h reference does not tell the consuming compiler which features this utility needs. Standalone consumers using the package’s h and render use the default factory.

import { h } from '@stencil/core';
import { useRender, type VNodeFactory } from 'finesoft-components/use-render';
const createElement: VNodeFactory = (tag, props, ...children) => (tag === 'svg' ? h('svg', props, ...children) : h(tag, props, ...children));
// Inside your component's render method:
return useRender({ createElement, defaultTagName: 'button', props: { children: 'Action' } });

The useRender.ComponentProps, ElementProps, Parameters, RenderProp, ReturnValue, and State types use Stencil VNodes and native events. React elements, React component functions and React hooks are not accepted as Stencil render overrides.

API reference

const element = useRender({
  // Input parameters
});

Parameters

useRender.Parameters

ReactElement | null

type useRenderState = {}

type useRenderComponentProps<
  ElementType extends React.ElementType,
  TState = {},
  RenderFunctionProps = HTMLProps,
> = React.ComponentPropsWithRef<ElementType> & {
  render?: ReactElement | ((props: RenderFunctionProps, state: TState) => ReactElement);
}

type useRenderElementProps =
  | (React.PropsWithoutRef<Props> & React.RefAttributes<R | any>)
  | Props
  | React.ComponentProps<React.ElementType>

type useRenderParameters<
  TState,
  RenderedElementType extends Element,
  Enabled extends boolean | undefined,
> = {
  /** The React element or a function that returns one to override the default element. */
  render?: UseRenderRenderProp<TState>;
  /** The ref to apply to the rendered element. */
  ref?: React.Ref<RenderedElementType>[] | React.Ref<RenderedElementType>;
  /**
   * The state of the component, passed as the second argument to the `render` callback.
   * State properties are automatically converted to data-* attributes.
   */
  state?: TState;
  /**
   * Custom mapping for converting state properties to data-* attributes.
   * @example { isActive: (value) => (value ? { 'data-is-active': '' } : null) }
   */
  stateAttributesMapping?: StateAttributesMapping<TState>;
  /**
   * Props to be spread on the rendered element.
   * They are merged with the internal props of the component, so that event handlers
   * are merged, `className` strings and `style` properties are joined, while other external props overwrite the
   * internal ones.
   */
  props?: Record<string, unknown>;
  /**
   * If `false`, the hook will skip most of its internal logic and return `null`.
   * This is useful for rendering a component conditionally.
   * @default true
   */
  enabled?: boolean | undefined;
  /**
   * The default tag name to use for the rendered element when `render` is not provided.
   * @default 'div'
   */
  defaultTagName?: keyof React.JSX.IntrinsicElements;
}

type useRenderRenderProp<TState = Record<string, unknown>> =
  | ReactElement
  | ((props: React.HTMLAttributes<any>, state: TState) => ReactElement)

type useRenderReturnValue = ReactElement | null

type HTMLProps<T = any> = React.HTMLAttributes<T> & { ref?: React.Ref<T> }

type UseRenderComponentProps<
  ElementType extends React.ElementType,
  State = {},
  RenderFunctionProps = HTMLProps,
> = React.ComponentPropsWithRef<ElementType> & {
  render?: ReactElement | ((props: RenderFunctionProps, state: State) => ReactElement);
}

type UseRenderElementProps =
  | (React.PropsWithoutRef<Props> & React.RefAttributes<R | any>)
  | Props
  | React.ComponentProps<React.ElementType>

type UseRenderParameters<
  State,
  RenderedElementType extends Element,
  Enabled extends boolean | undefined,
> = {
  /** The React element or a function that returns one to override the default element. */
  render?: UseRenderRenderProp<State>;
  /** The ref to apply to the rendered element. */
  ref?: React.Ref<RenderedElementType> | React.Ref<RenderedElementType>[];
  /**
   * The state of the component, passed as the second argument to the `render` callback.
   * State properties are automatically converted to data-* attributes.
   */
  state?: State;
  /**
   * Custom mapping for converting state properties to data-* attributes.
   * @example { isActive: (value) => (value ? { 'data-is-active': '' } : null) }
   */
  stateAttributesMapping?: StateAttributesMapping<State>;
  /**
   * Props to be spread on the rendered element.
   * They are merged with the internal props of the component, so that event handlers
   * are merged, `className` strings and `style` properties are joined, while other external props overwrite the
   * internal ones.
   */
  props?: Record<string, unknown>;
  /**
   * If `false`, the hook will skip most of its internal logic and return `null`.
   * This is useful for rendering a component conditionally.
   * @default true
   */
  enabled?: boolean | undefined;
  /**
   * The default tag name to use for the rendered element when `render` is not provided.
   * @default 'div'
   */
  defaultTagName?: keyof React.JSX.IntrinsicElements;
}

type UseRenderRenderProp<State = Record<string, unknown>> =
  | ReactElement
  | ((props: React.HTMLAttributes<any>, state: State) => ReactElement)

type UseRenderReturnValue = ReactElement | null

type UseRenderState = {}