Node-Red之创建一个简单的Node

创建一个简单的Node,可以将输入的数据转换成小写。

初始化一个npm 项目

1. 执行命令

npm init

执行过程：

# wjy @ qifang in ~/gitProjects/node-red-dev [21:49:17]
$ npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sensible defaults.

See `npm help json` for definitive documentation on these fields
and exactly what they do.

Use `npm install <pkg>` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
package name: (red-dev) node-red-contrib-example-lower-case
version: (1.0.0)
description: node-red-contrib-example-lower-case
entry point: (index.js) lower-case.js
test command:
git repository:
keywords:
author:
license: (ISC)
About to write to /Users/wjy/gitProjects/node-red-dev/package.json:

{
  "name": "node-red-contrib-example-lower-case",
  "version": "1.0.0",
  "description": "node-red-contrib-example-lower-case",
  "main": "lower-case.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC"
}


Is this OK? (yes)

这样一个简单的 npm 进行包管理的项目就算建成了。

在package.json文件中添加 node-red 的信息

将如下代码添加到package.json中

"node-red" : {
        "nodes": {
            "lower-case": "lower-case.js"
        }
    }

这里可以指名这个node包含了哪些文件。

更新后的package.json文件为：

{
  "name": "node-red-contrib-example-lower-case",
  "version": "1.0.0",
  "description": "node-red-contrib-example-lower-case",
  "main": "lower-case.j",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "node-red": {
    "nodes": {
      "lower-case": "lower-case.js"
    }
  },
  "author": "",
  "license": "ISC"
}

创建lower-case 节点的 js 和 html 文件

# wjy @ qifang in ~/gitProjects/node-red-dev/lower-case [22:01:03]
$ touch lower-case.js lower-case.html

# wjy @ qifang in ~/gitProjects/node-red-dev/lower-case [22:01:13]
$ ll
total 8
-rw-r--r--  1 wjy  staff     0B  3  2 22:01 lower-case.html
-rw-r--r--  1 wjy  staff     0B  3  2 22:01 lower-case.js
-rw-r--r--  1 wjy  staff   270B  3  2 21:50 package.json

这样一个Node的基本雏型已经有了。

编写 lower-case.js

module.exports = function(RED) {
    function LowerCaseNode(config) {
        RED.nodes.createNode(this,config);
        var node = this;
        node.on('input', function(msg) {
            msg.payload = msg.payload.toLowerCase();
            node.send(msg);
        });
    }
    RED.nodes.registerType("lower-case",LowerCaseNode);
}

• 这里将这个节点被封装为Node.js模块。 这个模块导出的函数，会在node-red启动并加载节点时被调用。

参数RED为模块提供对Node-RED运行时api的访问权限。

• 这里 node.on('input', function(msg) 将节点注册input事件的侦听器，每当消息到达节点时，这个事件就会被调用，然后它将有效的输入转换为小写，然后调用send函数以在流中传递消息。
• 这里 RED.nodes.registerType("lower-case",LowerCaseNode);用lower-case这个名字将 LowerCaseNode注册到Node-Red.

编写 lower-case.html

定义编辑器的节点
<script type="text/javascript">
    RED.nodes.registerType('lower-case',{
        category: 'function',
        color: '#a6bbcf',
        defaults: {
            name: {value:""}
        },
        inputs:1,
        outputs:1,
        icon: "file.png",
        label: function() {
            return this.name||"lower-case";
        }
    });
</script>

<script type="text/html" data-template-name="lower-case">
    <div class="form-row">
        <label for="node-input-name"><i class="fa fa-tag"></i> Name</label>
        <input type="text" id="node-input-name" placeholder="Name">
    </div>
</script>

<script type="text/html" data-help-name="lower-case">
    <p>A simple node that converts the message payloads into all lower-case characters</p>
</script>

将这个节点安装到当前的Node-Red

1. 在~/.node-red执行安装

npm i ~/gitProjects/node-red-dev/lower-case

执行过程：

# wjy @ bogon in ~/.node-red [22:34:12]
$ npm i ~/gitProjects/node-red-dev/lower-case
npm notice created a lockfile as package-lock.json. You should commit this file.
+ node-red-contrib-example-lower-case@1.0.0
added 1 package in 0.73s

2. 重新启动Node-Red

wjy @ wujiayudeMBP in ~/gitProjects/node-red on git:master x [22:34:58] 
$ npm run start

> node-red@1.2.3 start /Users/wjy/gitProjects/node-red
> node packages/node_modules/node-red/red.js

2 Mar 22:35:01 - [info] 

Welcome to Node-RED
===================

2 Mar 22:35:01 - [info] Node-RED version: v1.2.3
2 Mar 22:35:01 - [info] Node.js  version: v12.9.1
2 Mar 22:35:01 - [info] Darwin 20.3.0 x64 LE
2 Mar 22:35:01 - [info] Loading palette nodes
2 Mar 22:35:02 - [info] Settings file  : /Users/wjy/.node-red/settings.js
2 Mar 22:35:02 - [info] Context store  : 'default' [module=memory]
2 Mar 22:35:02 - [info] User directory : /Users/wjy/.node-red
2 Mar 22:35:02 - [warn] Projects disabled : editorTheme.projects.enabled=false
2 Mar 22:35:02 - [info] Flows file     : /Users/wjy/.node-red/flows_bogon.json
2 Mar 22:35:02 - [info] Creating new flow file
2 Mar 22:35:02 - [warn] 

---------------------------------------------------------------------
Your flow credentials file is encrypted using a system-generated key.

If the system-generated key is lost for any reason, your credentials
file will not be recoverable, you will have to delete it and re-enter
your credentials.

You should set your own key using the 'credentialSecret' option in
your settings file. Node-RED will then re-encrypt your credentials
file using your chosen key the next time you deploy a change.
---------------------------------------------------------------------

2 Mar 22:35:02 - [info] Starting flows
2 Mar 22:35:02 - [info] Started flows
2 Mar 22:35:02 - [info] Server now running at http://127.0.0.1:1880/

3. 查看新节点

配置使用这个简单的节点

1. 配置需要转换的数据

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2. 连接lower-case节点
3. 点击部署后开始执行

4. 查看结果

这样一个简单的Node就完成了。