Node Red Node Development

Node-RED Node Development

This skill provides patterns, APIs, and tools for developing custom Node-RED nodes.

When to Use This Skill

• Creating new Node-RED nodes from scratch
• Implementing node message handling and lifecycle
• Building edit dialogs with HTML/jQuery
• Creating configuration nodes for shared state
• Setting up node status indicators
• Packaging nodes for npm distribution

Quick Start

To scaffold a new node, run the initialization script:

# Regular node
python scripts/init_node.py my-node --path ./nodes

# Configuration node
python scripts/init_node.py my-config --config --path ./nodes

Node Architecture

Every Node-RED node consists of two files:

JavaScript File (.js)

Defines runtime behavior:

module.exports = function(RED) {
    function MyNode(config) {
        RED.nodes.createNode(this, config);
        var node = this;

        node.on('input', function(msg, send, done) {
            send = send || function() { node.send.apply(node, arguments) };
            try {
                // Process message
                send(msg);
                done();
            } catch (err) {
                done(err);
            }
        });

        node.on('close', function(removed, done) {
            // Cleanup resources
            done();
        });
    }
    RED.nodes.registerType("my-node", MyNode);
}

HTML File (.html)

Defines editor appearance with three <script> sections:

1. Node registration - RED.nodes.registerType()
2. Edit template - data-template-name
3. Help text - data-help-name

Key Patterns

Message Handling

node.on('input', function(msg, send, done) {
    // Node-RED 1.0+ compatibility
    send = send || function() { node.send.apply(node, arguments) };

    // Process and send
    msg.payload = transform(msg.payload);
    send(msg);

    // Signal completion (triggers done/error)
    done();
});

Error Handling

try {
    // risky operation
} catch (err) {
    if (done) {
        done(err);  // Triggers Catch nodes
    } else {
        node.error(err, msg);  // Node-RED 0.x
    }
}

Status Updates

node.status({ fill: "green", shape: "dot", text: "connected" });
node.status({ fill: "red", shape: "ring", text: "disconnected" });
node.status({});  // Clear status

Status properties:

• fill: "red", "green", "yellow", "blue", "grey"
• shape: "ring" (outline), "dot" (filled)
• text: Short string (under 20 characters)

Configuration Nodes

For shared connections/state:

// In config node
RED.nodes.registerType("my-server", MyServerNode, {
    credentials: {
        username: { type: "text" },
        password: { type: "password" }
    }
});

// In client node - reference config
this.server = RED.nodes.getNode(config.server);
if (this.server) {
    var connection = this.server.getConnection();
}

Cleanup (close event)

node.on('close', function(removed, done) {
    if (removed) {
        // Node disabled or deleted
    } else {
        // Flow redeploying
    }
    // Async cleanup with 15-second timeout
    disconnect(done);
});

HTML Edit Dialog

Input Naming Convention

• Regular nodes: id="node-input-<property>"
• Config nodes: id="node-config-input-<property>"

Form Structure

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

Editor Hooks

RED.nodes.registerType('my-node', {
    oneditprepare: function() {
        // Dialog opening - initialize widgets
    },
    oneditsave: function() {
        // User clicked Done - return false to cancel
    },
    oneditcancel: function() {
        // User clicked Cancel
    }
});

Packaging

package.json Structure

{
    "name": "@scope/node-red-my-nodes",
    "version": "1.0.0",
    "keywords": ["node-red"],
    "node-red": {
        "version": ">=2.0.0",
        "nodes": {
            "my-node": "nodes/my-node.js"
        }
    }
}

Important: Since January 2022, all new packages must use scoped names.

Local Testing

cd ~/.node-red
npm install /path/to/your/node
# Restart Node-RED

Reference Documentation

For detailed API documentation, consult the references directory:

• references/node-js-api.md - JavaScript API (send, receive, close, status, logging)
• references/node-html-api.md - HTML API (registration, edit dialog, help text)
• references/config-nodes.md - Configuration node patterns
• references/status-and-context.md - Status indicators and context storage
• references/packaging.md - npm packaging and publishing

To search for specific API patterns:

grep -r "pattern" references/

Common Mistakes to Avoid

1. Forgetting RED.nodes.createNode() - Must be called first in constructor
2. Not handling Node-RED 0.x compatibility - Use send = send || ... pattern
3. Blocking in input handler - Use async patterns for I/O
4. Not cleaning up in close - Always handle the close event
5. Wrong input ID prefix - node-input- vs node-config-input-
6. Mismatched type names - JS and HTML registerType must match
7. Missing credentials in both files - Define in both JS and HTML
8. Exceeding 15-second close timeout - Runtime will force-kill