beautiful-mermaid

Preflight

Before rendering, verify the CLI dependency is available:

node -e "require('beautiful-mermaid'); console.log('ok')"

If that fails, ask the user before installing globally. Explain that this installs the beautiful-mermaid package on their system via npm:

npm install -g beautiful-mermaid

If the user declines installation, stop. Do not proceed with inline render scripts until preflight passes.

Setup

Use via inline Node scripts. The library exposes two main functions:

• renderMermaidSVG(mermaidCode) — returns SVG string synchronously
• renderMermaidASCII(mermaidCode) — returns ASCII art string

Usage

Create a temp Node script to render diagrams:

const { renderMermaidSVG, renderMermaidASCII } = require('beautiful-mermaid')

const diagram = `graph TD
  A[Start] --> B{Decision}
  B -->|Yes| C[OK]
  B -->|No| D[End]`

const svg = renderMermaidSVG(diagram)
console.log(svg)

Run with node <file>.

Theming

Pass theme options as second argument:

renderMermaidSVG(code, { theme: 'tokyo-night' })
renderMermaidSVG(code, { bg: '#1e1e2e', fg: '#cdd6f4' })

Built-in themes: tokyo-night, catppuccin, nord, dracula, github, solarized, and more (15 total).

Minimal config: just bg and fg — rest derived via CSS color-mix().

For terminals, use ASCII rendering:

const ascii = renderMermaidASCII(code)
console.log(ascii)

Output handling

SVG output can be saved to file:

const fs = require('fs')
fs.writeFileSync('diagram.svg', svg)

Then display to user or reference the file path.

Supported diagram types

Type	Mermaid syntax
Flowchart	graph TD, graph LR, graph RL
State diagram	stateDiagram-v2
Sequence diagram	sequenceDiagram
Class diagram	classDiagram
ER diagram	erDiagram
XY Chart	xychart (bar, line, combined)