@codemirror/language

What is @codemirror/language?

The @codemirror/language package is part of the CodeMirror ecosystem, which provides a versatile text editor implemented in JavaScript for the browser. This specific package focuses on language support, offering tools and functionality to parse, analyze, and display code written in various programming languages. It allows for syntax highlighting, code parsing for autocompletion, and other language-specific features within the CodeMirror editor.

What are @codemirror/language's main functionalities?

Syntax Highlighting

This feature allows for syntax highlighting of JavaScript code within the CodeMirror editor. By importing the JavaScript language support from the package and applying it as an extension to the editor, the code within the editor is automatically highlighted according to the syntax of JavaScript.

import {javascript} from '@codemirror/lang-javascript';

let myEditor = new EditorView({
  doc: 'function myScript(){\n  console.log(\"Hello, world!\");\n}',
  extensions: [javascript()]
});

Code Parsing for Autocompletion

This code sample demonstrates how to enable autocompletion for JavaScript code. By combining the JavaScript language support with the autocomplete extension from CodeMirror, the editor can suggest completions based on the current context in the code, enhancing the coding experience.

import {javascript} from '@codemirror/lang-javascript';
import {autocomplete, startCompletion} from '@codemirror/autocomplete';

let myEditor = new EditorView({
  doc: 'console.',
  extensions: [javascript(), autocomplete(), EditorView.updateListener.of(update => {
    if (update.changes) startCompletion(myEditor);
  })]
});

Other packages similar to @codemirror/language

monaco-editor

The Monaco Editor is the code editor that powers VS Code, offering rich language support and development features. Compared to @codemirror/language, Monaco provides a more extensive set of features out of the box, including integrated syntax highlighting, autocompletion, and debugging for a wide range of languages. However, it might be heavier and more complex to integrate into web projects.

ace-builds

Ace is another popular code editor library that can be embedded in web pages and applications. Similar to @codemirror/language, it offers syntax highlighting, autocompletion, and other editing features for various programming languages. Ace is known for its extensibility and customizability, though it might not be as modern or as actively developed as CodeMirror.

README

@codemirror/language

[ WEBSITE | DOCS | ISSUES | FORUM | CHANGELOG ]

This package implements the language support infrastructure for the CodeMirror code editor.

The project page has more information, a number of examples and the documentation.

This code is released under an MIT license.

We aim to be an inclusive, welcoming community. To make that explicit, we have a code of conduct that applies to communication around the project.

Usage

Setting up a language from a Lezer parser looks like this:

import {parser} from "@lezer/json"
import {LRLanguage, continuedIndent, indentNodeProp,
        foldNodeProp, foldInside} from "@codemirror/language"

export const jsonLanguage = LRLanguage.define({
  name: "json",
  parser: parser.configure({
    props: [
      indentNodeProp.add({
        Object: continuedIndent({except: /^\s*\}/}),
        Array: continuedIndent({except: /^\s*\]/})
      }),
      foldNodeProp.add({
        "Object Array": foldInside
      })
    ]
  }),
  languageData: {
    closeBrackets: {brackets: ["[", "{", '"']},
    indentOnInput: /^\s*[\}\]]$/
  }
})

Often, you'll also use this package just to access some specific language-related features, such as accessing the editor's syntax tree...

import {syntaxTree} from "@codemirror/language"

const tree = syntaxTree(view)

... or computing the appriate indentation at a given point.

import {getIndentation} from "@codemirror/language"

console.log(getIndentation(view.state, view.state.selection.main.head))

Changelog

6.11.1 (2025-06-02)

Bug fixes

Fix an issue where indentation would sometimes miss nodes in mixed-language situations.