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Creating your first flow

Overview

This tutorial introduces the Node-RED editor and creates a flow the demonstrates the Inject, Debug and Function nodes.

1. Access the editor

With Node-RED running, open the editor in a web browser.

If you are using a browser on the same computer that is running Node-RED, you can access it with the url: http://localhost:1880.

If you are using a browser on another computer, you will need to use the ip address of the computer running Node-RED: http://<ip-address>:1880.

2. Add an Inject node

The Inject node allows you to inject messages into a flow, either by clicking the button on the node, or setting a time interval between injects.

Drag one onto the workspace from the palette.

Select the newly added Inject node to see information about its properties and a description of what it does in the Information sidebar pane.

3. Add a Debug node

The Debug node causes any message to be displayed in the Debug sidebar. By default, it just displays the payload of the message, but it is possible to display the entire message object.

4. Wire the two together

Connect the Inject and Debug nodes together by dragging between the output port of one to the input port of the other.

5. Deploy

At this point, the nodes only exist in the editor and must be deployed to the server.

Click the Deploy button.

With the Debug sidebar tab selected, click the Inject button. You should see numbers appear in the sidebar. By default, the Inject node uses the number of milliseconds since January 1st, 1970 as its payload.

6. Add a Function node

The Function node allows you to pass each message though a JavaScript function.

Delete the existing wire (select it and press delete on the keyboard).

Wire a Function node in between the Inject and Debug nodes.

Double-click on the Function node to bring up the edit dialog. Copy the following code into the function field:

// Create a Date object from the payload
var date = new Date(msg.payload);
// Change the payload to be a formatted Date string
msg.payload = date.toString();
// Return the message so it can be sent on
return msg;

Click Done to close the edit dialog and then click the deploy button.

Now when you click the Inject button, the messages in the sidebar will now be formatted is readable timestamps.


Summary

This flow demonstrates the basic concept of creating a flow. It shows how the Inject node can be used to manually trigger a flow, and how the Debug node displays messages in the sidebar. It also shows how the Function node can be used to write custom JavaScript to run against messages.

Source

The flow created in this tutorial is represented by the following json. To import it into the editor, copy it to your clipboard and then paste it into the Import dialog.

[{"id":"58ffae9d.a7005","type":"debug","name":"","active":true,"complete":false,"x":640,"y":200,"wires":[]},{"id":"17626462.e89d9c","type":"inject","name":"","topic":"","payload":"","repeat":"","once":false,"x":240,"y":200,"wires":[["2921667d.d6de9a"]]},{"id":"2921667d.d6de9a","type":"function","name":"Format timestamp","func":"// Create a Date object from the payload\nvar date = new Date(msg.payload);\n// Change the payload to be a formatted Date string\nmsg.payload = date.toString();\n// Return the message so it can be sent on\nreturn msg;","outputs":1,"x":440,"y":200,"wires":[["58ffae9d.a7005"]]}]

Next Steps