@nytimes/react-prosemirror

React ProseMirror

A fully featured library for safely integrating ProseMirror and React.

Installation

npm:

npm install @nytimes/react-prosemirror

yarn:

yarn add @nytimes/react-prosemirror

• The Problem
• The Solution
  • Rendering ProseMirror Views within React
    • useEditorEffect
    • useEditorEventCallback
    • useEditorEventListener
  • Building NodeViews with React
• API
  • ProseMirror
  • useEditorState
  • useEditorEventCallback
  • useEditorEventListener
  • useEditorEffect
  • useNodePos
  • useNodeViews
  • react

The Problem

React is a framework for developing reactive user interfaces. To make updates efficient, React separates updates into phases so that it can process updates in batches. In the first phase, application code renders a virtual document. In the second phase, the React DOM renderer finalizes the update by reconciling the real document with the virtual document. The ProseMirror View library renders ProseMirror documents in a single-phase update. Unlike React, it also allows built-in editing features of the browser to modify the document under some circumstances, deriving state updates from view updates rather than the other way around.

It is possible to use both React DOM and ProseMirror View, but using React DOM to render ProseMirror View components safely requires careful consideration of differences between the rendering approaches taken by each framework. The first phase of a React update should be free of side effects, which requires that updates to the ProseMirror View happen in the second phase. This means that during the first phase, React components actually have access to a different (newer) version of the EditorState than the one in the Editorview. As a result code that dispatches transactions may dispatch transactions based on incorrect state. Code that invokes methods of the ProseMirror view may make bad assumptions about its state that cause incorrect behavior or errors.

The Solution

There are two different directions to integrate ProseMirror and React: you can render a ProseMirror EditorView inside of a React component, and you can use React components to render ProseMirror NodeViews. This library provides tools for accomplishing both of these goals.

Rendering ProseMirror Views within React

This library provides a set of React contexts and hooks for consuming them that ensure safe access to the EditorView from React components. This allows us to build React applications that contain ProseMirror Views, even when the EditorState is lifted into React state, or a global state management system like Redux.

The simplest way to make use of these contexts is with the <ProseMirror/> component. The <ProseMirror/> component can be used controlled or uncontrolled, and takes a "mount" prop, used to specify which DOM node the ProseMirror EditorView should be mounted on.

import { EditorState } from "prosemirror-state";
import { schema } from "prosemirror-schema-basic";
import { ProseMirror } from "@nytimes/react-prosemirror";

const defaultState = EditorState.create({ schema });
export function ProseMirrorEditor() {
  // It's important that mount is stored as state,
  // rather than a ref, so that the ProseMirror component
  // is re-rendered when it's set
  const [mount, setMount] = useState<HTMLElement | null>(null);

  return (
    <ProseMirror mount={mount} defaultState={defaultState}>
      <div ref={setMount} />
    </ProseMirror>
  );
}

The EditorState can also easily be lifted out of the ProseMirror component and passed as a prop.

import { EditorState } from "prosemirror-state";
import { schema } from "prosemirror-schema-basic";
import { ProseMirror } from "@nytimes/react-prosemirror";

export function ProseMirrorEditor() {
  const [mount, setMount] = useState<HTMLElement | null>(null);
  const [state, setState] = useState(() => EditorState.create({ schema }));

  return (
    <ProseMirror
      mount={mount}
      state={state}
      dispatchTransaction={(tr) => {
        setState((s) => s.apply(tr));
      }}
    >
      <div ref={setMount} />
    </ProseMirror>
  );
}

The ProseMirror component will take care to ensure that the EditorView is always updated with the latest EditorState after each render cycle. Because synchronizing the EditorView is a side effect, it must happen in the effects phase of the React render lifecycle, after all of the ProseMirror component's children have run their render functions. This means that special care must be taken to access the EditorView from within other React components. In order to abstract away this complexity, React ProseMirror provides two hooks: useEditorEffect and useEditorEventCallback. Both of these hooks can be used from any children of the ProseMirror component.

useEditorEffect

Often, it's necessary to position React components relative to specific positions in the ProseMirror document. For example, you might have some widget that needs to be positioned at the user's cursor. In order to ensure that this positioning happens when the EditorView is in sync with the latest EditorState, we can use useEditorEffect.

// SelectionWidget.tsx
import { useRef } from "react";
import { useEditorEffect } from "@nytimes/react-prosemirror";

export function SelectionWidget() {
  const ref = useRef();

  useEditorEffect((view) => {
    if (!ref.current) return;

    const viewClientRect = view.dom.getBoundingClientRect();
    const coords = view.coordsAtPos(view.state.selection.anchor);

    ref.current.style.top = coords.top - viewClientRect.top;
    ref.current.style.left = coords.left - viewClientRect.left;
  });

  return (
    <div
      ref={ref}
      style={{
        position: "absolute",
      }}
    />
  );
}

// ProseMirrorEditor.tsx
import { EditorState } from "prosemirror-state";
import { schema } from "prosemirror-schema-basic";

import { SelectionWidget } from "./SelectionWidget.tsx";

export function ProseMirrorEditor() {
  const [mount, setMount] = useState<HTMLElement | null>(null);
  const [state, setState] = useState(() => EditorState.create({ schema }));

  return (
    <ProseMirror
      mount={mount}
      state={state}
      dispatchTransaction={(tr) => {
        setState((s) => s.apply(tr));
      }}
    >
      {/*
        We have to mount all components that need to access the
        EditorView as children of the ProseMirror component
      */}
      <SelectionWidget />
      <div ref={setMount} />
    </ProseMirror>
  );
}

useEditorEventCallback

It's also often necessary to dispatch transactions or execute side effects in response to user actions, like mouse clicks and keyboard events. Note: if you need to respond to keyboard events from within the contenteditable element, you should instead use useEditorEventListener.

However, if you need to dispatch a transaction in response to some event dispatched from a React component, like a tooltip or a toolbar button, you can use useEditorEventCallback to create a stable function reference that can safely access the latest value of the EditorView.

// BoldButton.tsx
import { toggleMark } from "prosemirror-commands";
import { useEditorEventCallback } from "@nytimes/react-prosemirror";

export function BoldButton() {
  const onClick = useEditorEventCallback((view) => {
    const toggleBoldMark = toggleMark(view.state.schema.marks.bold);
    toggleBoldMark(view.state, view.dispatch, view);
  });

  return <button onClick={onClick}>Bold</button>;
}

// ProseMirrorEditor.tsx
import { EditorState } from "prosemirror-state";
import { schema } from "prosemirror-schema-basic";

import { BoldButton } from "./BoldButton.tsx";

export function ProseMirrorEditor() {
  const [mount, setMount] = useState<HTMLElement | null>(null);
  const [state, setState] = useState(() => EditorState.create({ schema }));

  return (
    <ProseMirror
      mount={mount}
      state={state}
      dispatchTransaction={(tr) => {
        setEditorState((s) => s.apply(tr));
      }}
    >
      {/*
        We have to mount all components that need to access the
        EditorView as children of the ProseMirror component
      */}
      <BoldButton />
      <div ref={setMount} />
    </ProseMirror>
  );
}

useEditorEventListener

useEditorEventCallback produces functions that can be passed to React components as event handlers. If you need to listen to events that originate within the contenteditable node, however, those event listeners need to be registered with the EditorView's handleDOMEvents prop.

You can use the useEditorEventListener hook to accomplish this. It takes an eventType and an event listener. The event listener follows the usual semantics for ProseMirror's handleDOMEvents prop:

• Returning true or calling event.preventDefault will prevent other listeners from running.
• Returning true will not automatically call event.preventDefault; if you want to prevent the default contenteditable behavior, you must call event.preventDefault.

You can use this hook to implement custom behavior in your NodeViews:

import { useEditorEventListener } from "@nytimes/react-prosemirror";

function Paragraph({ node, children }) {
  const nodeStart = useNodePos();

  useEditorEventListener("keydown", (view, event) => {
    if (event.code !== "ArrowDown") {
      return false;
    }
    const nodeEnd = nodeStart + node.nodeSize;
    const { selection } = view.state;
    if (selection.anchor < nodeStart || selection.anchor > nodeEnd) {
      return false;
    }
    event.preventDefault();
    alert("No down keys allowed!");
    return true;
  });

  return <p>{children}</p>;
}

Building NodeViews with React

The other way to integrate React and ProseMirror is to have ProseMirror render NodeViews using React components. This is somewhat more complex than the previous section. This library provides a useNodeViews hook, a factory for augmenting NodeView constructors with React components, and react, a ProseMirror Plugin for maintaining the React component hierarchy.

useNodeViews takes a map from node name to an extended NodeView constructor. The NodeView constructor must return at least a dom attribute and a component attribute, but can also return any other NodeView attributes. Here's an example of its usage:

import {
  useNodeViews,
  useEditorEventCallback,
  NodeViewComponentProps,
  react,
} from "@nytimes/react-prosemirror";
import { EditorState } from "prosemirror-state";
import { schema } from "prosemirror-schema-basic";

// Paragraph is more or less a normal React component, taking and rendering
// its children. The actual children will be constructed by ProseMirror and
// passed in here. Take a look at the NodeViewComponentProps type to
// see what other props will be passed to NodeView components.
function Paragraph({ children }: NodeViewComponentProps) {
  const onClick = useEditorEventCallback((view) => view.dispatch(whatever));
  return <p onClick={onClick}>{children}</p>;
}

// Make sure that your ReactNodeViews are defined outside of
// your component, or are properly memoized. ProseMirror will
// teardown and rebuild all NodeViews if the nodeView prop is
// updated, leading to unbounded recursion if this object doesn't
// have a stable reference.
const reactNodeViews = {
  paragraph: () => ({
    component: Paragraph,
    // We render the Paragraph component itself into a div element
    dom: document.createElement("div"),
    // We render the paragraph node's ProseMirror contents into
    // a span, which will be passed as children to the Paragraph
    // component.
    contentDOM: document.createElement("span"),
  }),
};

const state = EditorState.create({
  schema,
  // You must add the react plugin if you use
  // the useNodeViews or useNodePos hook.
  plugins: [react()],
});

function ProseMirrorEditor() {
  const { nodeViews, renderNodeViews } = useNodeViews(reactNodeViews);
  const [mount, setMount] = useState<HTMLElement | null>(null);

  return (
    <ProseMirror mount={mount} nodeViews={nodeViews} defaultState={state}>
      <div ref={setMount} />
      {renderNodeViews()}
    </ProseMirror>
  );
}

API

ProseMirror

import type { EditorState, Plugin, Transaction } from "prosemirror-state";
import type { EditorProps, EditorView, Plugin } from "prosemirror-view";
import type { ReactNode } from "react";

interface ProseMirrorProps extends EditorProps {
  mount: HTMLElement | null;
  children?: ReactNode | null;
  defaultState?: EditorState;
  state?: EditorState;
  plugins?: readonly Plugin[];
  dispatchTransaction?(this: EditorView, tr: Transaction): void;
}

type ProseMirror = (props: ProseMirrorProps) => JSX.Element;

Renders a ProseMirror View.

The mount prop must be an actual HTMLElement instance. The JSX element representing the mount should be passed as a child to the ProseMirror component.

Consult the ProseMirror documentation for information about the other props.

Example usage:

function MyProseMirrorField() {
  const [mount, setMount] = useState(null);

  return (
    <ProseMirror mount={mount}>
      <div ref={setMount} />
    </ProseMirror>
  );
}

useEditorState

type useEditorState = () => EditorState;

Provides access to the current EditorState value.

useEditorEventCallback

type useEditorEventCallback = <T extends unknown[]>(
  callback: (view: EditorView | null, ...args: T) => void
) => void;

Returns a stable function reference to be used as an event handler callback.

The callback will be called with the EditorView instance as its first argument.

useEditorEventListener

type useEditorEventListener = <EventType extends DOMEventMap>(
  eventType: EventType,
  listener: (view: EditorView, event: DOMEventMap[EventType]) => boolean
) => void;

Attaches an event listener at the EditorView's DOM node. See the ProseMirror docs for more details.

useEditorEffect

type useEditorEffect = (
  effect: (editorView: EditorView | null) => void | (() => void),
  dependencies?: React.DependencyList
) => void;

Registers a layout effect to run after the EditorView has been updated with the latest EditorState and Decorations.

Effects can take an EditorView instance as an argument. This hook should be used to execute layout effects that depend on the EditorView, such as for positioning DOM nodes based on ProseMirror positions.

Layout effects registered with this hook still fire synchronously after all DOM mutations, but they do so after the EditorView has been updated, even when the EditorView lives in an ancestor component.

Example usage:

import { useRef } from "react";
import { useEditorEffect } from "@nytimes/react-prosemirror";

export function SelectionWidget() {
  const ref = useRef();

  useEditorEffect((view) => {
    if (!ref.current) return;

    const viewClientRect = view.dom.getBoundingClientRect();
    const coords = view.coordsAtPos(view.state.selection.anchor);

    ref.current.style.top = coords.top - viewClientRect.top;
    ref.current.style.left = coords.left - viewClientRect.left;
  });

  return (
    <div
      ref={ref}
      style={{
        position: "absolute",
      }}
    />
  );
}

useNodePos

type useNodePos = () => number;

Returns the node's current position in the document. Takes the place of ProseMirror's getPos function that gets passed to NodeView's, which is unsafe to use in React render functions.

This hook can only be used in React components rendered with useNodeViews.

useNodeViews

/**
 * Extension of ProseMirror's NodeViewConstructor type to include
 * `component`, the React component to used render the NodeView.
 * All properties other than `component` and `dom` are optional.
 */
type ReactNodeViewConstructor = (
  node: Node,
  view: EditorView,
  getPos: () => number,
  decorations: readonly Decoration[],
  innerDecorations: DecorationSource
) => {
  dom: HTMLElement | null;
  component: React.ComponentType<NodeViewComponentProps>;
  contentDOM?: HTMLElement | null;
  selectNode?: () => void;
  deselectNode?: () => void;
  setSelection?: (
    anchor: number,
    head: number,
    root: Document | ShadowRoot
  ) => void;
  stopEvent?: (event: Event) => boolean;
  ignoreMutation?: (mutation: MutationRecord) => boolean;
  destroy?: () => void;
  update?: (
    node: Node,
    decorations: readonly Decoration[],
    innerDecoration: DecorationSource
  ) => boolean;
};

type useNodeViews = (nodeViews: Record<string, ReactNodeViewConstructor>) => {
  nodeViews: Record<string, NodeViewConstructor>;
  renderNodeViews: () => ReactElement[];
};

Hook for creating and rendering NodeViewConstructors that are powered by React components. To use this hook, you must also include react in your EditorState.

component can be any React component that takes NodeViewComponentProps. It will be passed as props all of the arguments to the nodeViewConstructor except for editorView. NodeView components that need access directly to the EditorView should use the useEditorEventCallback, useEditorEventListener and useEditorEffect hooks to ensure safe access.

For contentful Nodes, the NodeView component will also be passed a children prop containing an empty element. ProseMirror will render content nodes into this element. Like in ProseMirror, the existence of a contentDOM attribute determines whether a NodeView is contentful (i.e. the NodeView has editable content that should be managed by ProseMirror).

react

type react = Plugin<Map<number, string>>;

A ProseMirror Plugin that assists in maintaining the correct hierarchy for React node views.

If you use useNodeViews or useNodePos, you must include this plugin in your EditorState.