mermaid-isomorphic
Render Mermaid diagrams in the browser or Node.js.
This is useful if you wish to render Mermaid diagrams in a Node.js or an isomorphic environment. If
you want to render Mermaid diagrams in the browser directly, use the
mermaid package directly.
Table of Contents
Installation
npm install mermaid-isomorphic
Outside of browsers mermaid-isomorphic uses Playwright. If you use this
outside of a browser, you need to install Playwright and a Playwright browser.
npm install playwright
npx playwright install --with-deps chromium
Usage
First, create a Mermaid renderer. Then use this renderer to render your diagrams.
import { createMermaidRenderer } from 'mermaid-isomorphic'
const renderer = createMermaidRenderer()
const diagram = `
graph TD;
A-->B;
A-->C;
B-->D;
C-->D;
`
const results = await renderer([diagram])
console.log(results)
Fonts
FontAwesome
Mermaid has support for
FontAwesome. This is
also supported by isomorphic-mermaid, but you need to load the FontAwesome CSS yourself when
serving the SVG.
Custom Fonts
By default mermaid-isomorphic uses the arial,sans-serif font family. This font family is mostly
compatible across all browsers and devices. If you wish to use a custom font, you need to specify
both the mermaidConfig.fontFamily and css options.
Browser
mermaid-isomorphic is intended for use in Node.js, but also provides a browser export. This means
it can be used in the browser, but it’s recommended to use the
mermaid package directly.
API
createMermaidRenderer(options?: CreateMermaidRendererOptions)
Create a Mermaid renderer.
The Mermaid renderer manages a browser instance. If multiple diagrams are being rendered
simultaneously, the internal browser instance will be re-used. If no diagrams are being rendered,
the browser will be closed.
Options
browserType (BrowserType): The Playwright browser to use. (default: chromium)launchOptions: (LaunchOptions): The options used to launch the browser.
Returns
A function that renders Mermaid diagrams in the browser. This function has arguments:
diagrams (string[]): An array of mermaid diagrams to render.options:
containerStyle (Partial<CSSStyleDeclaration>): A style to apply to the container used to
render the diagram. Certain styling is known to override the rendering behaviour. For example,
the maxWidth property affects gantt diagrams. (default:
{ maxHeight: '0', opacity: '0', overflow: 'hidden' })css (string | URL) A URL that points to a custom CSS file to load. Use this to load custom
fonts. This option is ignored in the browser. You need to include the CSS in your build
manually.screenshot (boolean): If true, a PNG screenshot of the diagram is included as a buffer. This
is only supported in Node.js.prefix (string): A custom prefix to use for Mermaid IDs (default: mermaid).mermaidOptions (MermaidConfig): A custom Mermaid configuration. By default fontFamily is
set to arial,sans-serif. This option is ignored in the browser. You need to call
mermaid.initialize() manually.
It returns a promise settled result with the render results. The render results have the following
properties:
description (string): The aria description of the diagram, if it has one.height (number): The height of the resulting SVG.id (string): The DOM id of the SVG node.screenshot (Buffer): The diagram SVG rendered as a PNG buffer. This is only added if the
screenshot option is true.svg (string): The diagram rendered as an SVG.title (string): The title of the rendered diagram, if it has one.width (number): The width of the resulting SVG.
Compatibility
This project is compatible with Node.js 18 or greater.
Contributing
Test fixtures are generated and verified using Linux. Rendering on other platforms may yield
slightly different results. Don’t worry about adding new fixtures, but don’t update existing ones
that cause CI to fail. Furthermore see my global
contributing guidelines.
License
MIT © Remco Haszing
