Mermaid in Markdown

Jan 06 2020

How to use Mermaid for flowcharts in blogs and with Hugo in Markdown documents.

Intro

Mermaid is a Markdown language to describe flow charts so you can easily describe things like this:

graph TD; A-->B; A-->C; B-->D; C-->D;

It is surprisingly easy to add Mermaid to your Markdown document. Either as HTML snippet or with a self made shortcut for the single site generator Hugo. I am sure its quite possible for other single site generators too.

Setup in any Markdown doc

Just add this to your markdown doc. HTML snippets are allowed in Markdown.

<div class="mermaid">
graph LR;
  A-->B;
</div>
<script async src="https://unpkg.com/mermaid@8.2.3/dist/mermaid.min.js"></script>

After the graph statement the Mermaid code can be added.

Setup a shortcut for Hugo

In Hugo add a file layouts/shortcuts/mermaid.html to your site base directory. Add this snippet to the file,

<!-- MermaidJS support -->

<div class="mermaid">
  {{.Inner}}
</div>
{{ if ($.Page.Params.mermaid) }}
<!-- MermaidJS support -->
<script async src="https://unpkg.com/mermaid/dist/mermaid.min.js"></script>
{{ end }}

The if statement checks if the front-matter parameter mermaid is set, otherwise the script is not used. This way the script will only be loaded if a parameter in the document specifically states so.

To activate mermaid in a document add this to your front-matter:

mermaid: true or mermaid = true

Add the mermaid code between the shortcut start and end. Note the additional / for the end code.

{ { < mermaid > } } (without the space)

graph TD;
  A-->B;
  A-->C;
  B-->D;
  C-->D;

{ { < /mermaid > } } (without the space)

Links:

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