named-slots

Slots for preact, react and solid in under 0.2Kb.

Slots allow to define "holes" in your components that can be filled with JSX. Inspired by slots in Vue/Svelte/Angular/WebComponents.

npm i named-slots

Quick start

Defining slots

Set the names of the slots you're using with defineSlots and use them in your JSX like <Slot name="slotName">, where want the slotted content to appear.

import { defineSlots } from "named-slots";

export const Card = ({ children }) => {
  const { Slot } = defineSlots(children, ["header", "content", "footer"]);

  return (
    <div className="card">
      <Slot name="header"></Slot>
      <Slot name="content">
        <div>Fallback content</div>
      </Slot>
      <div>
        <Slot name="footer">Fallback footer</Slot>
      </div>
    </div>
  );
};

Consuming components with Slots

Now you can slot content into your Card component. The only thing you need to do is set a slot="slotName" on the element you wish to slot in. To render only text or multiple elements, use the <template> element.

<Card>
  <div slot="header">This div is not semantic</div>
  <RandomComponent slot="content" />
  <template slot="footer">
    <div>One</div>
    <div>Two</div>
  </template>
</Card>

Fallback

When defining a <Slot> the content inside of it will be treated as fallback, in case nothing is slotted inside of that slot. If you do not want anything to be rendered, self-close the slot tag <Slot name="nofallback" />.

<ActionBar>
  <Slot name="left" /> {/* no fallback, will not render unless slotted*/}
  <Slot name="right">Loading...</Slot> {/* Will render "Loading..." until slotted */}
</ActionBar>

defineSlots and hasSlot

The defineSlots function handles the usage of slots. It takes the children prop of the component where it's used, and a string array of the slot names. If using Typescript add a as const to the string array so Typescript can check if the slot names are typed correctly.

defineSlots returns an object with the Slot component, but also a hasSlot function that allows to check if a slot has been slotted in, for conditional rendering.

export const DefinedCard = ({ children }: { children: Slottable }) => {
  const { Slot, hasSlot } = defineSlots(children, ["header", "content", "footer"] as const);

  const hasContent: boolean = hasSlot("content");

With Solid.js

Since solid does not use a VDOM it has a dedicated import.

import { Slot } from "named-slots/solid";

In addition every element with slot needs to be an HTML element, not a Solid component (or wrapped in one like the <template>). In the example above, <RandomComponent slot="content" /> would not work. <div ="content"><RandomComponent slot="content" /></div> would.

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