Flowcharts - Basic Syntax

All Flowcharts are composed of nodes, the geometric shapes and edges, the arrows or lines. The mermaid code defines the way that these nodes and edges are made and interact.

It can also accomodate different arrow types, multi directional arrows, and linking to and from subgraphs.

学習者ノート

Mermaid 開発陣はフローチャートとは言っているが、汎用の有向グラフとして取り扱うのがわかりやすい。

Important

Do not type the word “end” as a Flowchart node. Capitalize all or any one the letters to keep the flowchart from breaking, i.e, “End” or “END”. Or you can apply this workaround.

Node

A node (default)

flowchart LR id

Note

The id is what is displayed in the box.

A node with text

It is also possible to set text in the box that differs from the id. If this is done several times, it is the last text found for the node that will be used. Also if you define edges for the node later on, you can omit text definitions. The one previously defined will be used when rendering the box.

flowchart LR id1[This is the text in the box]

Graph

This statement declares the direction of the Flowchart.

This declares the flowchart is oriented from top to bottom (TD or TB).

flowchart TD Start --> Stop

This declares the flowchart is oriented from left to right (LR).

flowchart LR Start --> Stop

Flowchart Orientation

Possible FlowChart orientations are:

  • TB - top to bottom

  • TD - top-down/ same as top to bottom

  • BT - bottom to top

  • RL - right to left

  • LR - left to right

学習者ノート

実質的には四つだ。

Node shapes

学習者ノート

実際に描画させるとやたらスペースをとる形状がいくつかある。そういうものはテキストを設定しないで利用するのが本来想定されている用途なのだろう。

A node with round edges

flowchart LR id1(This is the text in the box)

A stadium-shaped node

flowchart LR id1([This is the text in the box])

A node in a subroutine shape

flowchart LR id1[[This is the text in the box]]

A node in a cylindrical shape

flowchart LR id1[(Database)]

A node in the form of a circle

flowchart LR id1((This is the text in the circle))

A node in an asymmetric shape

flowchart LR id1>This is the text in the box]

Currently only the shape above is possible and not its mirror. This might change with future releases.

A node (rhombus)

flowchart LR id1{This is the text in the box}

A hexagon node

flowchart LR id1{{This is the text in the box}}

Parallelogram

flowchart TD id1[/This is the text in the box/]

Parallelogram alt

flowchart TD id1[\This is the text in the box\]

Trapezoid

flowchart TD A[/Christmas\]

Trapezoid alt

flowchart TD B[\Go shopping/]

Special characters that break syntax

It is possible to put text within quotes in order to render more troublesome characters. As in the example below:

flowchart LR id1["This is the (text) in the box"]

Entity codes to escape characters

It is possible to escape characters using the syntax exemplified here.

flowchart LR A["A double quote:#quot;"] -->B["A dec char:#9829;"]

Numbers given are base 10, so # can be encoded as #35;. It is also supported to use HTML character names.

Subgraphs

学習者ノート

部分グラフの構文は次のとおりだ。

subgraph title
    graph definition
end

An example below:

flowchart TB c1-->a2 subgraph one a1-->a2 end subgraph two b1-->b2 end subgraph three c1-->c2 end

You can also set an explicit id for the subgraph.

flowchart TB c1-->a2 subgraph ide1 [one] a1-->a2 end

flowcharts

With the graphtype flowchart it is also possible to set edges to and from subgraphs as in the flowchart below.

flowchart TB c1-->a2 subgraph one a1-->a2 end subgraph two b1-->b2 end subgraph three c1-->c2 end one --> two three --> two two --> c2

Direction in subgraphs

With the graphtype flowcharts you can use the direction statement to set the direction which the subgraph will render like in this example.

flowchart LR subgraph TOP direction TB subgraph B1 direction RL i1 -->f1 end subgraph B2 direction BT i2 -->f2 end end A --> TOP --> B B1 --> B2

Interaction

It is possible to bind a click event to a node, the click can lead to either a javascript callback or to a link which will be opened in a new browser tab.

Note

This functionality is disabled when using securityLevel='strict' and enabled when using securityLevel='loose'.

click nodeId callback
click nodeId call callback()

  • nodeId is the id of the node

  • callback is the name of a javascript function defined on the page displaying the graph, the function will be called with the nodeId as parameter.

Examples of tooltip usage below:

<script>
  var callback = function(){
      alert('A callback was triggered');
  }
</script>

学習者ノート

モダンな JavaScript コードを書いても問題ない。

The tooltip text is surrounded in double quotes. The styles of the tooltip are set by the class .mermaidTooltip.

flowchart LR A-->B B-->C C-->D click A callback "Tooltip for a callback" click B "http://www.github.com" "This is a tooltip for a link" click A call callback() "Tooltip for a callback" click B href "http://www.github.com" "This is a tooltip for a link"

Success

The tooltip functionality and the ability to link to urls are available from version 0.5.2.

Due to limitations with how Docsify handles JavaScript callback functions, an alternate working demo for the above code can be viewed at this jsfiddle.

Links are opened in the same browser tab/window by default. It is possible to change this by adding a link target to the click definition (_self, _blank, _parent and _top are supported):

flowchart LR A-->B B-->C C-->D D-->E click A "http://www.github.com" _blank click B "http://www.github.com" "Open this in a new tab" _blank click C href "http://www.github.com" _blank click D href "http://www.github.com" "Open this in a new tab" _blank

Beginners tip, a full example using interactive links in a html context:

<body>
  <div class="mermaid">
    flowchart LR
        A-->B
        B-->C
        C-->D
        click A callback "Tooltip"
        click B "http://www.github.com" "This is a link"
        click C call callback() "Tooltip"
        click D href "http://www.github.com" "This is a link"
  </div>

  <script>
    var callback = function(){
        alert('A callback was triggered');
    }
    var config = {
        startOnLoad:true,
        flowchart:{
            useMaxWidth:true,
            htmlLabels:true,
            curve:'cardinal',
        },
        securityLevel:'loose',
    };

    mermaid.initialize(config);
  </script>
</body>

学習者ノート

環境によっては対話的操作が制限される。例えば VS Code の Markdown Preview Mermaid Support ではツールチップは表示されない。

Comments

Comments can be entered within a flow diagram, which will be ignored by the parser. Comments need to be on their own line, and must be prefaced with %% (double percent signs). Any text after the start of the comment to the next newline will be treated as a comment, including any flow syntax

flowchart LR %% this is a comment A -- text --> B{node} A -- text --> B -- text2 --> C

Styling and classes

Styling a node

It is possible to apply specific styles such as a thicker border or a different background color to a node.

flowchart LR id1(Start)-->id2(Stop) style id1 fill:#f9f,stroke:#333,stroke-width:4px style id2 fill:#bbf,stroke:#f66,stroke-width:2px,color:#fff,stroke-dasharray: 5 5

Classes

More convenient than defining the style every time is to define a class of styles and attach this class to the nodes that should have a different look.

A class definition looks like the example below:

classDef className fill:#f9f,stroke:#333,stroke-width:4px;

Attachment of a class to a node is done as per below:

class nodeId1 className;

It is also possible to attach a class to a list of nodes in one statement:

class nodeId1,nodeId2 className;

A shorter form of adding a class is to attach the classname to the node using the ::: operator as per below:

flowchart LR A:::someclass --> B classDef someclass fill:#f96;

学習者ノート

クラス名がコロンの後に来るので違和感がある。

Css classes

It is also possible to predefine classes in css styles that can be applied from the graph definition as in the example below:

Example style

<style>
    .cssClass > rect{
        fill:#FF0000;
        stroke:#FFFF00;
        stroke-width:4px;
    }
</style>

Example definition

flowchart LR; A-->B[AAA<span>BBB</span>] B-->D class A cssClass

学習者ノート

span タグが活きていない？

Default class

If a class is named default it will be assigned to all classes without specific class definitions.

classDef default fill:#f9f,stroke:#333,stroke-width:4px;

Basic support for fontawesome

It is possible to add icons from fontawesome.

The icons are accessed via the syntax fa:#icon class name#.

flowchart TD B["fa:fa-twitter for peace"] B-->C[fa:fa-ban forbidden] B-->D(fa:fa-spinner); B-->E(A fa:fa-camera-retro perhaps?)

学習者ノート

Font Awesome のことは深入りしないことにする。

Configuration

Is it possible to adjust the width of the rendered flowchart.

This is done by defining mermaid.flowchartConfig or by the CLI to use a json file with the configuration. How to use the CLI is described in the mermaidCLI page. mermaid.flowchartConfig can be set to a JSON string with config parameters or the corresponding object.

mermaid.flowchartConfig = {
    width: 100%
}