Code

editor.tsx

import 'prosekit/basic/style.css'

import { createEditor } from 'prosekit/core'
import { ProseKit } from 'prosekit/react'
import { useMemo } from 'react'

import { defineExtension } from './extension'
import Toolbar from './toolbar'

export default function Editor() {
  const editor = useMemo(() => {
    return createEditor({ extension: defineExtension() })
  }, [])

  return (
    <ProseKit editor={editor}>
      <div className='box-border h-full w-full min-h-36 overflow-y-hidden overflow-x-hidden rounded-md border border-solid border-gray-200 shadow dark:border-zinc-700 flex flex-col bg-white dark:bg-neutral-900'>
        <Toolbar />
        <div className='relative w-full flex-1 box-border overflow-y-scroll'>
          <div ref={editor.mount} className='ProseMirror box-border min-h-full px-[max(4rem,_calc(50%-20rem))] py-8 outline-none outline-0 [&_span[data-mention="user"]]:text-blue-500 [&_span[data-mention="tag"]]:text-violet-500 [&_pre]:text-white [&_pre]:bg-zinc-800'></div>
        </div>
      </div>
    </ProseKit>
  )
}

extension.ts

import {
  defineBaseKeymap,
  defineDoc,
  defineParagraph,
  defineText,
  union,
} from 'prosekit/core'
import { defineHeading } from 'prosekit/extensions/heading'

export function defineExtension() {
  return union(
    defineBaseKeymap(),
    defineDoc(),
    defineText(),
    defineParagraph(),
    defineHeading(),
  )
}

export type EditorExtension = ReturnType<typeof defineExtension>

toolbar.tsx

import { useEditor } from 'prosekit/react'

import Button from './button'
import type { EditorExtension } from './extension'

export default function Toolbar() {
  const editor = useEditor<EditorExtension>({ update: true })

  return (
    <div className='z-2 box-border border-zinc-200 dark:border-zinc-800 border-solid border-l-0 border-r-0 border-t-0 border-b flex flex-wrap gap-1 p-2 items-center'>
      <Button
        pressed={editor.nodes.heading.isActive({ level: 1 })}
        disabled={!editor.commands.toggleHeading.canExec({ level: 1 })}
        onClick={() => editor.commands.toggleHeading({ level: 1 })}
        tooltip="Heading 1"
      >
        H1
      </Button>

      <Button
        pressed={editor.nodes.heading.isActive({ level: 2 })}
        disabled={!editor.commands.toggleHeading.canExec({ level: 2 })}
        onClick={() => editor.commands.toggleHeading({ level: 2 })}
        tooltip="Heading 2"
      >
        H2
      </Button>

      <Button
        pressed={editor.nodes.heading.isActive({ level: 3 })}
        disabled={!editor.commands.toggleHeading.canExec({ level: 3 })}
        onClick={() => editor.commands.toggleHeading({ level: 3 })}
        tooltip="Heading 3"
      >
        H3
      </Button>
    </div>
  )
}

button.tsx

import {
  TooltipContent,
  TooltipRoot,
  TooltipTrigger,
} from 'prosekit/react/tooltip'
import type { ReactNode } from 'react'

export default function Button({
  pressed,
  disabled,
  onClick,
  tooltip,
  children,
}: {
  pressed?: boolean
  disabled?: boolean
  onClick?: VoidFunction
  tooltip?: string
  children: ReactNode
}) {
  return (
    <TooltipRoot>
      <TooltipTrigger className='block'>
        <button
          data-state={pressed ? 'on' : 'off'}
          disabled={disabled}
          onClick={() => onClick?.()}
          onMouseDown={(event) => event.preventDefault()}
          className='outline-unset focus-visible:outline-unset flex items-center justify-center rounded-md p-2 font-medium transition focus-visible:ring-2 text-sm focus-visible:ring-zinc-900 dark:focus-visible:ring-zinc-300 disabled:pointer-events-none min-w-9 min-h-9 disabled:opacity-50 hover:disabled:opacity-50 bg-transparent hover:bg-zinc-100 dark:hover:bg-zinc-800 data-[state=on]:bg-gray-200 dark:data-[state=on]:bg-gray-700'
        >
          {children}
          {tooltip ? <span className="sr-only">{tooltip}</span> : null}
        </button>
      </TooltipTrigger>
      {tooltip ? (
        <TooltipContent className='z-50 overflow-hidden rounded-md border border-solid bg-zinc-900 dark:bg-zinc-50 px-3 py-1.5 text-xs text-zinc-50 dark:text-zinc-900 shadow-sm [&:not([data-state])]:hidden will-change-transform data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=open]:fade-in-0 data-[state=closed]:fade-out-0 data-[state=open]:zoom-in-95 data-[state=closed]:zoom-out-95 data-[state=open]:animate-duration-150 data-[state=closed]:animate-duration-200 data-[side=bottom]:slide-in-from-top-2 data-[side=bottom]:slide-out-to-top-2 data-[side=left]:slide-in-from-right-2 data-[side=left]:slide-out-to-right-2 data-[side=right]:slide-in-from-left-2 data-[side=right]:slide-out-to-left-2 data-[side=top]:slide-in-from-bottom-2 data-[side=top]:slide-out-to-bottom-2'>
          {tooltip}
        </TooltipContent>
      ) : null}
    </TooltipRoot>
  )
}