例 1

```mermaid
sequenceDiagram
Alice->John: Hello John, how are you?
loop Every minute
John-->Alice: Great!
end
```

sequenceDiagram
    Alice->John: Hello John, how are you?
    loop Every minute
        John-->Alice: Great!
    end

例 2

```mermaid
sequenceDiagram
　　Alice->>John: Hello John, how are you ?
　　John-->>Alice: Great!
　　Alice->>John: Hung,you are better .
　　John-->>Alice: yeah, Just not bad.
```

sequenceDiagram
 　　Alice->>John: Hello John, how are you ?
 　　John-->>Alice: Great!
 　　Alice->>John: Hung,you are better .
 　　John-->>Alice: yeah, Just not bad.

例 3

```mermaid
sequenceDiagram
　　participant John
　　participant Alice
　　Alice-xJohn:Hello John,how are you?
　　John-->>Alice:Great!
```

sequenceDiagram
　　participant John
　　participant Alice
　　Alice-xJohn:Hello John,how are you?
　　John-->>Alice:Great!

例 4

消息的语法：
实线或者虚线的使用：
[Actor][Arrow][Actor]:Message text\
Arrow 的六种样式：

• ->
• –>
• ->>
• –>>
• -x
• –x
  ```mermaid
  sequenceDiagram
  Alice->John: Hello John, how are you ?
  John-->Alice:Great!
  Alice->>John: dont borther me !
  John-->>Alice:Great!
  Alice-xJohn: wait!
  John--xAlice: Ok!
  ```

sequenceDiagram
 Alice->John: Hello John, how are you ?
 John-->Alice:Great!
 Alice->>John: dont borther me !
 John-->>Alice:Great!
 Alice-xJohn: wait!
 John--xAlice: Ok!

例 5

便签

给序列图增加便签：\
具体规则：\
[right of | left of | over][Actor]:Text\

```mermaid
sequenceDiagram
　　participant John
　　Note left of John: Text in note
```

sequenceDiagram
　　participant John
　　Note left of John: Text in note

跨越两个 Actor 的便签

```mermaid
sequenceDiagram
Alice->>John:Hello John, how are you?
Note over Alice,John:A typical interaction
```

sequenceDiagram
Alice->>John:Hello John, how are you?
Note over Alice,John:A typical interaction

循环 Loops

也可以使用循环，具体规则如下：

loop Loop text
... statements...
end

```mermaid
sequenceDiagram
　　Alice->>John: Hello!
　　loop Reply every minute
　　　　John->>Alice:Great!
　　end
```

sequenceDiagram
　　Alice->>John: Hello!
　　loop Reply every minute
　　　　John->>Alice:Great!
　　end

选择 ALT

在序列图中选择的表达。规则如下：

alt Describing text
...statements...
else
...statements...
end

或者使用 opt(推荐在没有 else 的情况下使用)

opt Describing text
...statements...
end

```mermaid
sequenceDiagram
　　Alice->>Bob: Hello Bob, how are you?
　　alt is sick
　　　　Bob->>Alice:not so good :(
　　else is well
　　　　Bob->>Alice:Feeling fresh like a daisy:)
　　end
　　opt Extra response
　　　　Bob->>Alice:Thanks for asking
　　end
```

sequenceDiagram
 　　Alice->>Bob: Hello Bob, how are you?
 　　alt is sick
 　　　　Bob->>Alice:not so good :(
 　　else is well
 　　　　Bob->>Alice:Feeling fresh like a daisy:)
 　　end
 　　opt Extra response
 　　　　Bob->>Alice:Thanks for asking
 　　end

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