Type Definitions

Enhance offers a set of common type definitions that can be used with JSDoc comments to annotate critical parts of your Enhance project. These will help when writing custom elements, API middleware, and other critical pieces of an Enhance project.

Save @enhance/types to your development dependencies:

npm i -D @enhance/types

Usage Examples

If your editor supports auto-complete and error detection (like VS Code’s Intellisense) via commented types, you can indicate that a function adheres to a certain type.

Custom Element

Use the EnhanceElemFn type when defining custom elements in /app/elements/. This will provide hinting for the argument passed to your function, including the html function and state object.

 * @type {import('@enhance/types').EnhanceElemFn}
export default function TodoItem({
  state: { attrs }
}) {
  const todoId = attrs['todo-id']
  const completed = typeof attrs.completed === 'string'

  return html`
    <div class="flex">
        ${completed ? 'checked' : ''}

API Handler

In this case, mark this “Todos” API GET handler as the type EnhanceApiFn and gain hinting for the request and response objects:

/** @type {import('@enhance/types').EnhanceApiFn} */
export async function get(request) {
  console.log(`Handling ${request.path}...`)

  const todos = [
    { title: 'todo 1'},
    { title: 'todo 2', completed: true },

  const response = {
    json: { todos }

  return response

Note that the JSDoc comment can be a single line, but there cannot be an extra line between the comment and the method declaration.

Head Function

Your app’s Head function can also be typed with the request argument and a return type of string by adding EnhanceHeadFn.

import { getLinkTag } from '@enhance/arc-plugin-styles/get-styles'

/** @type {import('@enhance/types').EnhanceHeadFn} */
export default function Head({ store, status, req, error }) {
  const { path } = req
  const title = `Todos — ${path}`

  return `
    <!DOCTYPE html>
      <meta charset="utf-8">

Community Resources

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