Prism react editor

Code editor component for React apps

What?

This is a rewrite of Prism code editor using React and hooks. It's a lightweight, extensible code editor optimized for fast load times with many optional extensions.

Contents

• Installation
• Demo
• Examples
• Basic usage
• Props
• Extensions
  • Creating your own
• Editor API
  • Properties
    • DOM Elements
  • Methods
  • Extensions property
• Utilities
• Prism
• Languages
• Styling
  • Themes
• Performance
• Contributing

Installation

npm i prism-react-editor

You must already have react and react-dom version 16.8.0 or greater installed.

Demo

Prism code editor's demo. There's no demo for this React rewrite since its behavior is nearly identical.

Examples

• Usage in forms
• Next.js example
• Preact example
• Relative line numbers
• Custom cursor

Basic usage

Below is an example of a simple JSX editor.

import { Editor } from "prism-react-editor"
import { BasicSetup } from "prism-react-editor/setups"

// Adding the JSX grammar
import "prism-react-editor/prism/languages/jsx"

// Adds comment toggling and auto-indenting for JSX
import "prism-react-editor/languages/jsx"

import "prism-react-editor/layout.css"
import "prism-react-editor/themes/github-dark.css"

// Required by the basic setup
import "prism-react-editor/search.css"

function MyEditor() {
  return (
    <Editor language="jsx" value="const foo = 'bar'">
      {editor => <BasicSetup editor={editor} />}
    </Editor>
  )
}

Props

| Name | Type | Description | | ------------------- | ------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | language | string | Language used for syntax highlighting. Defaults to text. | | tabSize | number | Tab size used for indentation. Defaults to 2. | | insertSpaces | boolean | Whether the editor should insert spaces for indentation. Defaults to true. Requires useDefaultCommands() extension to work. | | lineNumbers | boolean | Whether line numbers should be shown. Defaults to true. | | readOnly | boolean | Whether the editor should be read only. Defaults to false. | | wordWrap | boolean | Whether the editor should have word wrap. Defaults to false. | | value | string | Initial value to display in the editor. | | rtl | boolean | Whether the editor uses right to left directionality. Defaults to false. Requires extra CSS from prism-react-editor/rtl-layout.css to work. | | style | Omit<React.CSSProperties, "tabSize"> | Allows adding inline styles to the container element. | | textareaProps | React.TextareaHTMLAttributes | Allows adding props to the editor's textarea element. Unsupported props | | ref | React.ForwardedRef<PrismEditor> | Ref allowing access to the editor instance. | | onUpdate | (value: string, editor: PrismEditor) => void | Function called after the editor updates. | | onSelectionChange | (selection: InputSelection, value: string, editor: PrismEditor) => void | Function called when the editor's selection changes. | | onTokenize | (tokens: TokenStream, language: string, value: string, editor: PrismEditor) => void | Function called before the tokens are stringified to HTML. | | children | (editor: PrismEditor) => React.ReactNode | Callback used to render extensions. |

Pitfall

This component is not controlled, and the value prop should be treated like an initial value. Do not change the value prop in the onUpdate handler. This will cause multiple issues and negatively impact performance.

// counterexample: do not do this
function MyEditor() {
  const [value, setValue] = useState("const foo = 'bar'")

  return (
    <Editor language="jsx" value={value} onUpdate={setValue} />
  )
}

Extensions

To keep the core light, most functionality is added by optional extensions.

There are extensions adding:

• Many common commands
• Bracket matching and rainbow brackets
• Tag matching
• Indentation guides
• Search, regex search and replace
• Selection match highlighting
• A copy button
• Read-only code folding
• Custom undo/redo
• And more...

Many commonly used extensions are added by BasicSetup, but if you want to fully customize which extensions are added. Below it's shown how to import most extensions.

import { Editor, PrismEditor } from "prism-react-editor"
import "prism-react-editor/prism/languages/jsx"
import "prism-react-editor/layout.css"
// Needed for the search widget
import "prism-react-editor/search.css"
// Needed for the copy button
import "prism-react-editor/copy-button.css"

import { useBracketMatcher } from "prism-react-editor/match-brackets"
import { useHightlightBracketPairs } from "prism-react-editor/highlight-brackets"
import { IndentGuides } from "prism-react-editor/guides"
import { useHighlightSelectionMatches, useSearchWidget } from "prism-react-editor/search"
import { useHighlightMatchingTags, useTagMatcher } from "prism-react-editor/match-tags"
import { useCursorPosition } from "prism-react-editor/cursor"
import { useDefaultCommands, useEditHistory } from "prism-react-editor/commands"
import { useCopyButton } from "prism-react-editor/copy-button"
import { useOverscroll } from "prism-react-editor/overscroll"

function MyExtensions({ editor }: { editor: PrismEditor }) {
  useBracketMatcher(editor)
  useHightlightBracketPairs(editor)
  useOverscroll(editor)
  useTagMatcher(editor)
  useHighlightMatchingTags(editor)
  useDefaultCommands(editor)
  useEditHistory(editor)
  useSearchWidget(editor)
  useHighlightSelectionMatches(editor)
  useCopyButton(editor)
  useCursorPosition(editor)

  return <IndentGuides editor={editor} />
}

function MyEditor() {
  return (
    <Editor language="jsx" value="const foo = 'bar'">
      {editor => <MyExtensions editor={editor} />}
    </Editor>
  )
}

Note: The extensions will rerender whenever the editor components props change. The editor object does not change reference between rerenders, so if you memoize the extensions component with React.memo, the extensions won't rerender causing potential issues. If you're using the React Compiler, you might need to add the "use no memo" directive to the extensions component so the compiler doesn't memoize it.

Lazy loading extensions is also possible for code splitting. It's not recommended to lazy load useBracketMatcher and you might want IndentGuides to be present on first render. All other extensions will work perfectly fine while lazy loaded.

import { lazy } from "react"

const LazyExtensions = lazy(() => import("./extensions"))

function MyExtensions({ editor }: { editor: PrismEditor }) {
  useBracketMatcher(editor)

  return <IndentGuides editor={editor} />
}

function MyEditor() {
  return (
    <Editor language="jsx" value="const foo = 'bar'">
      {editor => (
        <>
          <MyExtensions editor={editor} />
          <LazyExtensions editor={editor} />
        </>
      )}
    </Editor>
  )
}

Creating your own

If you need to do anything more than adding an onUpdate or onSelectionChange prop, you should consider creating your own extension.

import { useLayoutEffect, useEffect } from "react"
import { PrismEditor, Editor } from "prism-react-editor"
import { BasicSetup } from "prism-react-editor/setups"

function MyExtension({ editor }: { editor: PrismEditor }) {
  // Layout effects will run before the editor has mounted
  useLayoutEffect(() => {
    return editor.on("selectionChange", selection => {
      console.log("Selection changed:", selection)
    })
  }, [])

  useEffect(() => {
    // The editor has mounted now
    editor.textarea!.focus()
  }, [])

  // The elements returned are added to the editor's overlays
  // Keep in mind that they will get some default styles
  return (
    <>
      <div>My overlay</div>
      <BasicSetup editor={editor} />
    </>
  )
}

function MyEditor() {
  return (
    <Editor language="jsx" value="const foo = 'bar'">
      {editor => <MyExtension editor={editor} />}
    </Editor>
  )
}

Editor API

The editor object you can access with the children property has many useful properties and methods.

Properties

• value: string: Current value of the editor.
• activeLine: number: Line number of the line with the cursor. You can index into editor.lines to get the DOM node for the active line.
• inputCommandMap: Record<string, InputCommandCallback | null | undefined>: Record mapping an input to a function called when that input is typed.
• keyCommandMap: Record<string, KeyCommandCallback | null | undefined>: Record mapping KeyboardEvent.key to a function called when that key is pressed.
• extensions: Object: Object storing some of the extensions added to the editor. Read more.
• props: EditorProps: The component props passed to the editor.
• focused: boolean. Whether the textarea is focused.
• tokens: TokenStream. Current tokens displayed in the editor.

DOM Elements

• container: HTMLDivElement: This is the outermost element of the editor.
• wrapper: HTMLDivElement: Element wrapping the lines and overlays.
• lines: HTMLCollectionOf<HTMLDivElement>: Collection containing the overlays as the first element, followed by all code lines.
• textarea: HTMLTextAreaElement: Underlying textarea in the editor.

Methods

• update(): void: Forces the editor to update. Can be useful after modifying a grammar for example.
• getSelection(): InputSelection: Gets the selectionStart, selectionEnd and selectionDirection for the textarea.
• setSelection(start: number, end?: number, direction?: "backward" | "forward" | "none"): void: Sets the selection for the textarea and synchronously updates the selection signal.
• on<T extends keyof EditorEventMap>(name: T, listener: EditorEventMap[T]): () => void: Adds a listener for editor events and returns a cleanup function. Intended to be used by extensions inside a useLayoutEffect or useEffect hook.

Extensions property

Multiple extensions have an entry on editor.extensions allowing you to interact with the extension.

• matchBrackets: BracketMatcher: Allows access to all brackets found in the editor along with which are paired together.
• matchTags: TagMatcher: Allows access to all tags found in the editor along with which tags are paired together.
• cursor: Cursor: Allows you to get the cursor position relative to the editor's overlays and to scroll the cursor into view.
• searchWidget: SearchWidget: Allows you to open or close the search widget.
• history: EditHistory: Allows you to clear the history or navigate it.
• folding: ReadOnlyCodeFolding: Allows access to the full unfolded code and to toggle folded ranges.

Utilities

The prism-react-editor/utils entry point exports various utilities for inserting text, changing the selection, finding token elements and more.

Prism

The Prism instance used by this library is exported from prism-react-editor/prism. This allows you to add your own Prism grammars or perform syntax highlighting outside of an editor. All modules under prism-react-editor/prism can run outside the browser in for example Node.js to do syntax highlighting on the server. API docs.

Languages

Prism supports syntax highlighting for hundreds of languages, but none of them are imported by default. You need to choose which languages to import. Importing prism-react-editor/prism/languages/javascript for example will register the JavaScript grammar through side effects.

If you need access to many languages, you can import the following entry points:

• prism-react-editor/prism/languages for all languages (~180kB)
• prism-react-editor/prism/languages/common for 42 common languages (~30kB)

This library also supports auto-indenting, comment toggling and self-closing tags for most of these languages. For it to work, you need the useDefaultCommands() hook (or the basic setup) and to import the behavior for the language.

The easiest way is to import all languages at ~3.6kB gzipped. You can dynamically import this since it's usually not needed before the page has loaded.

import("prism-react-editor/languages")

You can also import prism-react-editor/languages/common instead to support a subset of common languages at less than 2kB gzipped.

Lastly, if you only need support for a few languages, you can do individual imports, for example prism-react-editor/languages/html. Read more.

Styling

This library does not inject any CSS into the webpage, instead you must import them. If the default styles don't work for you, you can import your own styles instead.

• prism-react-editor/layout.css is the layout for the editor.
• prism-react-editor/scrollbar.css adds a custom scrollbar to desktop Chrome and Safari you can color with --editor__bg-scrollbar.
• prism-react-editor/copy-button.css adds styling for the copy button.
• prism-react-editor/search.css adds styling for the search widget.
• prism-react-editor/rtl-layout.css adds support for the rtl prop.

By default, the editor's height will fit the content, so you might want to add a height or max-height to .prism-code-editor depending on your use case.

Themes

here are currently 13 different themes you can import, one of them being from prism-react-editor/themes/github-dark.css.

You can also dynamically import themes into your JavaScript.

import { loadTheme } from "prism-react-editor/themes"

const isDark = matchMedia("(prefers-color-scheme: dark)").matches

loadTheme(isDark ? "github-dark" : "github-light").then(theme => {
  console.log(theme)
})

If none of the themes fit your website, use one of them as an example to help implement your own.

Performance

Manual DOM manipulation has been kept almost everywhere. This rewrite therefore has very similar performance to the original which would not be the case if only JSX was used.

Contributing

Contributions are welcome. To test your changes during development, run pnpm dev or npm run dev to run the test site.