How to Declare Global Variable in Node Red

In this post i will step through  2 Different method on how to  Declare a Global Variable in Node Red.

Prior to that , you will need to create 2 Flows to Test out the Global Variable Later

Click the “+” Icon on your right to Create 2 Flow , and provide  names to both

In My Case I name it Flow 1 and Flow 2

Method 1

For Method 1 I will use Change node to Set / declare the global Variable

 

Step 1

In Flow 1 , Drag out and inject Node  and Configure as Below

Pass a String Value ” This is A Global String 1 ” to the msg.payload

Step 2

In  Flow 1 .Drag Out a Change Node  and Configure as below . The Configuration shows that it will pass the data from msg.payload to firstGlobalString

After this Step , you will be able to use “firstGlobalString” Variable in All Flows reside in Node Red

Step 3

Connect the Nodes together.

Now you have completed the node where when trigger it will inject ” This is A Global String 1 ” to the msg.payload. The Change Node will read the msg.payload Value

and Pass the Value into the global Variable “firstGlobalString”

 

Step 4

Retrieve the  global Variable “firstGlobalString” Value

In Flow 2 ,Drag out the inject Node and Configure as below .

The Inject Node will pass the  “firstGlobalString “global Variable value into msg.payload

 

Step 5

In Flow 2 Drag Out a Debug Node , and configure as Below

Step 6

Joint  the Nodes, trigger both inject node  at  Flow 2 and Observe the results

Results

 

Method 2

For Method 2 I will use Function node to Set / declare the Global Variable

 

Step 1

In Flow 1 Drag out and inject Node  and Configure as Below

Pass a String Value ” This is A Global String 2 ” to the msg.payload

Step 2

In Flow 1 Drag Out a Function Node  and Configure as below . The Configuration shows that it will pass the data from msg.payload to global.secondGlobalString

After this Step , you will be able to use “secondGlobalString” global variable for all flow in Node Red

Copy and paste the code below and paste it into the Text Area inside the  “On Message ” Tab

Code as below

Step 5

In Flow 2 Drag Out a Debug Node , and configure as Below

 

Step 6

In Flow 2 Joint  the Nodes, trigger both inject node and Observe the results

 

 

Results

 

check out How to Create Flow Variable in Node red