import mermaid from '@diplodoc/mermaid-extension';
import transform from '@diplodoc/transform';

const {result} = await transform(`
\`\`\`mermaid
graph TD
    A[Christmas] -->|Get money| B(Go shopping)
\`\`\`
`, {
    plugins: [
        mermaid.transform({ bundle: false })
    ]
});

Add mermaid runtime to your final page

<html>
    <head>
        <!-- Read more about '_assets/mermaid-extension.js' in 'MarkdownIt transform plugin' section -->
        <script src="_assets/mermaid-extension.js" async />
    </head>
    <body style="background: #000">
        ${result.html}
        <script>
            // Read more about 'mermaidJsonp' in 'Prepared Mermaid runtime' section
            window.mermaidJsonp = window.mermaidJsonp || [];
            window.mermaidJsonp.push((mermaid) => {
                mermaid.initialize({ theme: 'dark' });
                mermaid.run();
            });
        </script>
    </body>
</html>

Prepared Mermaid runtime

The problem with Mermaid is that it has big bundle size. The most expected behavior is loading it asynchronously. But if we want to disable Mermaid's startOnLoad option, then we don't know when the Mermaid will be initialized.

Prepared Mermaid runtime designed to solve this problem. We disable Mermaid's startOnLoad option to precise control render step. Then we add mermaidJsonp global callback to handle Mermaid's loading.

Also, we limit exposed Mermaid API by two methods:

initialize - configure mermaid before next render
run - start diagrams rendering

Usage example:

window.mermaidJsonp = window.mermaidJsonp || [];

// This callback will be called when runtime is loaded
window.mermaidJsonp.push((mermaid) => {
    mermaid.initialize({ theme: 'dark' });
    mermaid.run();
});

// You can configure more that one callback
window.mermaidJsonp.push((mermaid) => {
    console.log('Render diagrams');
});

Custom initialize options

Exposed mermaid.initialize method has extra configuration options:

zoom - Enable diagram zoom and explore feature. Can be boolean or object with inner props.
(Default: false)
- showMenu - Show navigation menu.
  (Default: false)
- bindKeys - Enable wasd controls.
  Use w/a/s/d to explore diagram, e/q to zoom in/out and r to reset diagram position.
  (Default: false)
- maximumScale - Maximum zoom scale.
  (Default: 5)
- resetOnBlur - Reeset diagram position on outher click.
  (Default: false)

MarkdownIt transform plugin

Plugin for @diplodoc/transform package.

Configuration:

runtime - name of runtime script which will be exposed in results script section.
(Default: _assets/mermaid-extension.js)
bundle - boolean flag to enable/disable copying of bundled runtime to target directory.
Where target directore is <transformer output option>/<plugin runtime option>
Default: true
classes - additional classes which will be added to Mermaid's diagrams.
Example: my-own-class and-other-class

React hook and component for smart control of Mermaid

Simplifies Mermaid control with react

import React from 'react'
import { transform } from '@diplodoc/transform'
import mermaid from '@diplodoc/mermaid-extension/plugin'
import { MermaidRuntime } from '@diplodoc/mermaid-extension/react'

const MERMAID_RUNTIME = 'extension:mermaid';

const Doc: React.FC = ({ content }) => {
    const result = transform(content, {
      plugins: [
        // Initialize plugin for client/server rendering
        mermaid.transform({
          // Do not touch file system
          bundle: false,
          // Set custom runtime name for searching in result scripts
          runtime: MERMAID_RUNTIME
        })
      ]
    })

    // Load mermaid only if one or more diagram should be rendered
    if (result.script.includes(MERMAID_RUNTIME)) {
      // Load oversized mermaid runtime asyncronously
      import('@diplodoc/mermaid-extension/runtime')
    }

    return <div dangerouslySetInnerHTML={{ __html: result.html }} />
}

export const App: React.FC = ({ theme }) => {
    return <>
        <Doc content={`
            \`\`\`mermaid
            graph TD
                A[Christmas] -->|Get money| B(Go shopping)
                B --> C{Let me think}
            \`\`\`
        `}/>
        <MermaidRuntime
            zoom={{
              showMenu: true,
              bindKeys: true,
              resetOnBlur: true,
            }}
        />
    </>
}

Keywords

mermaid

markdown-it

FAQs

What is @diplodoc/mermaid-extension?

Is @diplodoc/mermaid-extension well maintained?

Package last updated on 16 Jul 2025

Did you know?

Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.

Install

@diplodoc/mermaid-extension