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将消息属性设置为固定值

问题

您想将消息属性设置为固定值。

解决方案

使用 Change 节点来设置消息的属性。

示例

[{"id":"d72dc4ce.89b368","type":"inject","z":"535331d8.55c1f","name":"","topic":"","payload":"","payloadType":"date","repeat":"","crontab":"","once":false,"x":140,"y":80,"wires":[["78075f19.e0174"]]},{"id":"78075f19.e0174","type":"change","z":"535331d8.55c1f","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"Hello World!","tot":"str"}],"action":"","property":"","from":"","to":"","reg":false,"x":340,"y":80,"wires":[["78dc7c25.b90d54"]]},{"id":"78dc7c25.b90d54","type":"debug","z":"535331d8.55c1f","name":"","active":true,"console":"false","complete":"false","x":550,"y":80,"wires":[]}]

讨论

Change 节点可用于设置消息的属性。

该节点支持设置各种 JavaScript 类型以及一些 Node-RED 特定类型。

  • 字符串: "hello world"
  • 数字: 42
  • 布尔值: true/false
  • 时间戳: 从纪元(1970年1月1日)以来的当前时间,以毫秒为单位
  • JSON: 将解析为其对象表示的 JSON 字符串
  • 缓冲区: Node.js 的 Buffer 对象

它还支持根据上下文属性的值、其他消息属性或 JSONata 表达式将属性设置为某个值。