# Solid

A custom element built with elements-kit is just `class extends HTMLElement` registered via `customElements.define`. Solid renders it fine at runtime, but Solid's `JSX.IntrinsicElements` is independent of elements-kit's, so you need a small augmentation to get typed props, narrowed `ref`, and editor autocomplete on the Solid side.

```ts
// shared element — built once, used anywhere
import { defineElement } from "elements-kit/custom-elements";
import { reactive } from "elements-kit/signals";

export class XCounter extends HTMLElement {
  @reactive() count = 0;
}

defineElement("x-counter", XCounter);
```

## Source the prop shape from the class

Three type helpers exported from `elements-kit/custom-elements` read the raw platform surface off the class. All three take the constructor (`typeof XCounter`); `PropertiesOf` also accepts an instance type.

| Helper                          | Shape                                                                                                            | Use when                                                                                 |
| ------------------------------- | ---------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------- |
| `PropertiesOf<typeof XCounter>` | Public instance fields, all optional — the `HTMLElement` surface is dropped; `Slot`-typed fields accept a `Node` | Typing property assignments — prop bindings, wrappers, helper functions                  |
| `AttributesOf<typeof XCounter>` | Every key of `static [ATTRIBUTES]`, valued `string \| null`                                                      | Typing the raw HTML attribute surface — `setAttribute`, server-rendered markup           |
| `EventsOf<typeof XCounter>`     | The `static events` map, verbatim — event name to event type                                                     | Typing `addEventListener`, framework event bindings, `HTMLElementEventMap` augmentations |

For most Solid wiring `PropertiesOf<typeof XCounter>` is enough.

## Augment Solid's `JSX.IntrinsicElements`

```ts
import type { JSX } from "solid-js";
import type { PropertiesOf } from "elements-kit/custom-elements";
import type { XCounter } from "./x-counter";

declare module "solid-js" {
  namespace JSX {
    interface IntrinsicElements {
      "x-counter": JSX.HTMLAttributes<XCounter> & PropertiesOf<typeof XCounter>;
    }
  }
}

// <x-counter count={5} ref={(el) => …} />  — el: XCounter
```

`JSX.HTMLAttributes<XCounter>` provides the standard HTML attribute surface (`class`, `id`, `onClick`, …) and a `ref` narrowed to `XCounter`.

## Co-locate the augmentation with the class

Put the `declare module "solid-js"` block in the same file as the element class. Importing the class then brings the augmentation along — consumers don't have to remember to write it themselves.

```ts
// x-counter.ts
import { defineElement, type PropertiesOf } from "elements-kit/custom-elements";
import { reactive } from "elements-kit/signals";

export class XCounter extends HTMLElement {
  @reactive() count = 0;
}

defineElement("x-counter", XCounter);

declare module "solid-js" {
  namespace JSX {
    interface IntrinsicElements {
      "x-counter": JSX.HTMLAttributes<XCounter> & PropertiesOf<typeof XCounter>;
    }
  }
}
```

## Typed `document.querySelector` and `createElement`

Independent of any JSX framework, augmenting the global `HTMLElementTagNameMap` gives you typed lookups in plain DOM code:

```ts
declare global {
  interface HTMLElementTagNameMap {
    "x-counter": XCounter;
  }
}

const el = document.querySelector("x-counter"); // XCounter | null
```

Worth doing alongside the Solid augmentation.

***

## See also

* [Custom Elements overview](/custom-elements)
* [React integration](/integrations/react)
* [Vue integration](/integrations/vue)
* [Angular integration](/integrations/angular)
* [Svelte integration](/integrations/svelte)
* [Lit integration](/integrations/lit)
* [Astro integration](/integrations/astro)
* [Marko integration](/integrations/marko)
* [Qwik integration](/integrations/qwik)