-
Notifications
You must be signed in to change notification settings - Fork 154
Creating Nodes
TODO:
- Add windows specific instructions if needed.
- Add more information on how to test nodes and provide a test harness. There is a test helper for nodes in the main repo which is reused by node-red-nodes repo that needs documenting and maybe exposing better.
Nodes get created when a flow is deployed, they may send and receive some messages whilst the flow is running and they get deleted when the next flow is deployed.
They typically consist of a pair of files; a JavaScript file that defines what the node does, and an html file that defines the node's properties, edit dialog and help text.
A package.json file is used to package it all together as an npm module.
This example will show how to create a node that converts message payloads to all lower-case characters.
Ensure you have the recommended LTS version of Node.js installed on your system. As of this writing this is version LTS 8.x which includes npm version 5.x.
Create a directory where you will develop your code. Within that directory, create the following files:
package.jsonlower-case.jslower-case.html
This is a standard file used by Node.js modules to describe their contents.
To generate a standard package.json file you can use the command npm init.
This will ask a series of questions to help create the initial content for the
file, using sensible defaults where it can. When prompted, give it the name
node-red-contrib-example-lower-case.
Once generated, you must added a node-red section:
{
"name" : "node-red-contrib-example-lower-case",
...
"node-red" : {
"nodes": {
"lower-case": "lower-case.js"
}
}
}This tells the runtime what node files the module contains.
For more information about how to package your node, including requirements on naming and other properties that should be set before publishing your node, refer to the packaging guide.
Note: Please do not publish this example node to npm!
{% highlight javascript %}
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);
}
{% endhighlight %}
The node is wrapped as a Node.js module. The module exports a function that gets called
when the runtime loads the node on start-up. The function is called with a single
argument, RED, that provides the module access to the Node-RED runtime api.
The node itself is defined by a function, LowerCaseNode that gets called whenever
a new instance of the node is created. It is passed an object containing the
node-specific properties set in the flow editor.
The function calls the RED.nodes.createNode function to initialise the features
shared by all nodes. After that, the node-specific code lives.
In this instance, the node registers a listener to the input event which gets
called whenever a message arrives at the node. Within this listener, it changes
the payload to lower case, then calls the send function to pass the message
on in the flow.
Finally, the LowerCaseNode function is registered with the runtime using the
name for the node, lower-case.
If the node has any external module dependencies, they must be included in the dependencies
section of its package.json file.
For more information about the runtime part of the node, see here.
{% highlight html %}
<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/x-red" data-template-name="lower-case">
<div class="form-row">
<label for="node-input-name"><i class="icon-tag"></i> Name</label>
<input type="text" id="node-input-name" placeholder="Name">
</div>
</script>
<script type="text/x-red" data-help-name="lower-case">
<p>A simple node that converts the message payloads into all lower-case characters</p>
</script>
{% endhighlight %}
A node's HTML file provides the following things:
- the main node definition that is registered with the editor
- the edit template
- the help text
In this example, the node has a single editable property, name. Whilst not
required, there is a widely used convention to this property to help distinguish
between multiple instances of a node in a single flow.
For more information about the editor part of the node, see here.
Nodes get created when a flow is deployed, they may send and receive some messages whilst the flow is running and they get deleted when the next flow is deployed.
They typically consist of a pair of files; a JavaScript file that defines what the node does, and an html file that defines the node's properties, edit dialog and help text.
A package.json file is used to package it all together as an npm module.
This example will show how to create a node that converts message payloads to all lower-case characters.
Ensure you have the recommended LTS version of Node.js installed on your system. As of this writing this is version LTS 8.x which includes npm version 5.x.
Create a directory where you will develop your code. Within that directory, create the following files:
package.jsonlower-case.jslower-case.html
This is a standard file used by Node.js modules to describe their contents.
To generate a standard package.json file you can use the command npm init.
This will ask a series of questions to help create the initial content for the
file, using sensible defaults where it can. When prompted, give it the name
node-red-contrib-example-lower-case.
Once generated, you must added a node-red section:
{
"name" : "node-red-contrib-example-lower-case",
...
"node-red" : {
"nodes": {
"lower-case": "lower-case.js"
}
}
}This tells the runtime what node files the module contains.
For more information about how to package your node, including requirements on naming and other properties that should be set before publishing your node, refer to the packaging guide.
Note: Please do not publish this example node to npm!
{% highlight javascript %}
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);
}
{% endhighlight %}
The node is wrapped as a node module. The module exports a function that gets called
when the runtime loads the node on start-up. The function is called with a single
argument, RED, that provides the module access to the Node-RED runtime api.
The node itself is defined by a function, LowerCaseNode that gets called whenever
a new instance of the node is created. It is passed an object containing the
node-specific properties set in the flow editor.
The function calls the RED.nodes.createNode function to initialise the features
shared by all nodes. After that, the node-specific code lives.
In this instance, the node registers a listener to the input event which gets
called whenever a message arrives at the node. Within this listener, it changes
the payload to lower case, then calls the send function to pass the message
on in the flow.
Finally, the LowerCaseNode function is registered with the runtime using the
name for the node, lower-case.
If the node has any external module dependencies, they must be included in the dependencies
section of its package.json file.
For more information about the runtime part of the node, see here.
{% highlight html %}
<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/x-red" data-template-name="lower-case">
<div class="form-row">
<label for="node-input-name"><i class="icon-tag"></i> Name</label>
<input type="text" id="node-input-name" placeholder="Name">
</div>
</script>
<script type="text/x-red" data-help-name="lower-case">
<p>A simple node that converts the message payloads into all lower-case characters</p>
</script>
{% endhighlight %}
A node's HTML file provides the following things:
- the main node definition that is registered with the editor
- the edit template
- the help text
In this example, the node has a single editable property, name. Whilst not
required, there is a widely used convention to this property to help distinguish
between multiple instances of a node in a single flow.
For more information about the editor part of the node, see here.
Once you have created a basic node module as described above, you can install it into your Node-RED runtime.
To test a node module locally using npm 5.x, the npm install <folder> command can be used. This allows you
to develop the node in a local directory and have it linked into a local node-red install during development.
In your node-red user directory, typically ~/.node-red, run:
npm install <location of node module>
For example, if your node is located at ~/dev/node-red-contrib-example-lower-case you would type the following:
cd ~/.node-red
npm install ~/dev/node-red-contrib-example-lower-case
This creates a symbolic link to your node module project directory in ~/.node-red/node_modules so that Node-RED will discover the node when it starts. Any changes to the node's file can be picked up by simply restarting Node-RED.
If you are using an older version of npm, you can create a symbolic link manually to your project. To do so:
cd ~/.node-red/node_modules
ln -s ~/dev/node-red-contrib-example-lower-case .
package.json file located in your user directory. To prevent this, use the npm --no-save option.