rodemirror

React component for CodeMirror 6

Features

• Lightweight, 829B minified + gzipped
• Simple, wraps CodeMirror's view and state and gets out of your way
• Efficient, only renders when necessary and uses StateEffect to update the editor state on prop changes. The view and state are never recreated.

Installation

npm install rodemirror @codemirror/state @codemirror/view

Usage

Use the CodeMirror component:

import { basicSetup } from '@codemirror/basic-setup'
import { javascript } from '@codemirror/lang-javascript'
import { oneDark } from '@codemirror/theme-one-dark'
import { useMemo } from 'react'
import CodeMirror from 'rodemirror'

const Editor = () => {
  const extensions = useMemo(() => [basicSetup, oneDark, javascript()], [])

  return <CodeMirror extensions={extensions} />
}

The useMemo is so that the extensions are not recreated each time, which would cause unnecessary editor transactions. You'll want to do the same with the selection prop.

Uncontrolled

Create an uncontrolled component for reading values.

import { basicSetup } from '@codemirror/basic-setup'
import { javascript } from '@codemirror/lang-javascript'
import { Extension } from '@codemirror/state'
import { oneDark } from '@codemirror/theme-one-dark'
import { useMemo, useState } from 'react'
import CodeMirror from 'rodemirror'

const Editor = () => {
  const extensions = useMemo<Extension[]>(
    () => [basicSetup, oneDark, javascript()],
    [],
  )

  const defaultValue = "console.log('Hello world!')"
  // remove if you do not need the value
  const [value, setValue] = useState(defaultValue)

  return (
    <CodeMirror
      value={defaultValue}
      onUpdate={(v) => {
        if (v.docChanged) {
          setValue(v.state.doc.toString())
        }
      }}
      extensions={extensions}
    />
  )
}

Controlled/Separate Reading and Writing

A truly controlled value is not recommended as you will be overwriting the entire document on each input and the editor will become very slow. This also does not work with features such as autocomplete. If you must pass in a controlled value, you can separate the reading and writing values and only update when necessary:

import { useMemo, useState, useEffect } from 'react'
import CodeMirror from 'rodemirror'
import { Extension } from '@codemirror/state'
import { basicSetup } from '@codemirror/basic-setup'
import { oneDark } from '@codemirror/theme-one-dark'
import { javascript } from '@codemirror/lang-javascript'

const Editor = ({ shouldAddLogOnChange }) => {
  const Editor = ({
    shouldAddLogOnChange,
  }: {
    shouldAddLogOnChange: boolean
  }) => {
    const extensions = useMemo<Extension[]>(
      () => [basicSetup, oneDark, javascript()],
      []
    )

    const defaultValue = "console.log('Hello world!')"
    const [readValue, setReadValue] = useState(defaultValue)
    const [writeValue, setWriteValue] = useState(defaultValue)

    // example
    useEffect(() => {
      setWriteValue(`${readValue}\nconsole.log('hello world')`)
    }, [shouldAddLogOnChange])

    return (
      <CodeMirror
        value={writeValue}
        onUpdate={(v) => {
          if (v.docChanged) {
            setReadValue(v.state.doc.toString())
          }
        }}
        extensions={extensions}
      />
    )
  }

EditorView and EditorState (Complex Use Cases)

Unless you are performing complex actions, you likely do not need this. You can use callbacks to keep EditorView and EditorState. You can keep the EditorView in a useState like so:

import { EditorView } from '@codemirror/view'

const Editor = () => {
  const extensions = useMemo(() => [basicSetup, oneDark, javascript()], [])

  const [editorView, setEditorView] = useState<EditorView | null>(null)

  return (
    <CodeMirror
      extensions={extensions}
      onEditorViewChange={(editorView) => setEditorView(editorView)}
    />
  )
}

The same applies to EditorState, though it can also be accessed from EditorView.state.

Examples

See the examples for how the editor can be used.