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    7.2.1 • Public • Published

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    demo @

    npm install react-codemirror2 codemirror --save

    react-codemirror2 ships with the notion of an uncontrolled and controlled component. UnControlled consists of a simple wrapper largely powered by the inner workings of codemirror itself, while Controlled will demand state management from the user, preventing codemirror changes unless properly handled via value. The latter will offer more control and likely be more appropriate with redux heavy apps.

    uncontrolled usage

    import {UnControlled as CodeMirror} from 'react-codemirror2'
      value='<h1>I ♥ react-codemirror2</h1>'
        mode: 'xml',
        theme: 'material',
        lineNumbers: true
      onChange={(editor, data, value) => {

    controlled usage

    import {Controlled as CodeMirror} from 'react-codemirror2'
      onBeforeChange={(editor, data, value) => {
      onChange={(editor, data, value) => {

    requiring codemirror resources

    codemirror comes as a peer dependency, meaning you'll need to require it in your project in addition to react-codemirror2. This prevents any versioning conflicts that would arise if codemirror came as a dependency through this wrapper. It's been observed that version mismatches can cause difficult to trace issues such as sytax highlighting disappearing without any explicit errors/warnings

    • additional

    Since codemirror ships mostly unconfigured, the user is left with the responsibility for requiring any additional resources should they be necessary. This is often the case when specifying certain language modes and themes. How to import/require these assets will vary according to the specifics of your development environment. Below is a sample to include the assets necessary to specify a mode of xml (HTML) and a material theme.

    note that the base codemirror.css file is required in all use cases

    @import 'codemirror/lib/codemirror.css';
    @import 'codemirror/theme/material.css';
    import CodeMirror from 'react-codemirror2';


    prop type default components description
    autoCursor boolean true Controlled UnControlled should component cursor position correct when value changed
    autoScroll boolean true Controlled UnControlled should component scroll cursor position into view when value changed
    className string Controlled UnControlled pass through class class="react-codemirror2 className"
    defineMode object Controlled UnControlled pass a custom mode via {name: 'custom', fn: myModeFn}
    detach boolean UnControlled should component ignore new props
    options object Controlled UnControlled codemirror configuration
    value string *Controlled UnControlled * component value must be managed for controlled components

    props cont. (wrapped codemirror programming api)

    will programmatically set cursor to the position specified

        line: 5,
        ch: 10
      onCursor={(editor, data) => {}}

    will programmatically scroll to the specified coordinate

        x: 50,
        y: 50
      onScroll={(editor, data) => {}}
    • selection={{ranges: array<{anchor, head}>, focus?: boolean} - setSelections

    will programmatically select the ranges specified

        ranges: [{
          anchor: {ch: 8, line: 5},
          head: {ch: 37, line: 5}
        focus: true // defaults false if not specified
      onSelection={(editor, data) => {}}


    event components description
    editorDidAttach(editor) UnControlled component is now responding to new props
    editorDidConfigure(editor) Controlled UnControlled component configuration has been set
    editorDidDetach(editor) UnControlled component is now ignoring new props
    editorDidMount(editor, [next]) Controlled UnControlled * invoking optional next will trigger editorDidConfigure
    editorWillUnmount(editor) Controlled UnControlled invoked before componentWillUnmount
    onBeforeChange(editor, data, value, [next]) Controlled UnControlled * if used, next is returned via UnControlled and must be invoked to trigger onChange
    onChange(editor, data, value) Controlled UnControlled the component value has been changed

    events cont. wrapped codemirror events


    • Is server side rendering supported?

    Yes. react-codemirror2 will prevent rendering in absence of navigator. You can also force the component to not render via a PREVENT_CODEMIRROR_RENDER global.

    • How can I get the instance?

    The recommended technique to get the instance is to persist the editor returned via event callbacks. There is no static method to get it on demand, e.g. CodeMirror.getInstance(). Example...

    constructor() {
      this.instance = null;
    render() {
      <CodeMirror editorDidMount={editor => { this.instance = editor }}/>
    • How can I have a resizable editor?

    Check out bokuweb/re-resizable. Wrapping your component with <Resizable/>'s works well


    Pull Requests are welcome. Be mindful of the available scripts below to help submitting a well-received contribution.

    • npm run start to run the app on localhost:8000
    • npm run test to ensure tests continue to pass
    • npm run build to generate the demo bundle

    note that it's necessary to bump the package.json version prior to final npm run build so we can grab the proposed new version as seen in the demo header. Also note, the core changes are to be made in src/index.tsx as ./index.js and ./index.d.ts are generated

    MIT © 2020 scniro


    npm i react-codemirror2

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