# Sum 2 nodes in a function

**URL:** <https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648>\
**Category:** General\
**Created:** [17 March 2023 06:19 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648 "2023-03-17T06:19:37Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![kroonp](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kroonp/32/68249_2.png) [@kroonp](https://discourse.nodered.org/u/kroonp)\
**Post date:** [17 March 2023 06:19 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/1 "2023-03-17T06:19:37Z")

</div>

hello all,  
I have tried in different ways to add 2 numbers in a function. I can not do it.  
I also have very little experience with functions in Nodende.  
Who wants to help me get this done.

Thankx,  
Peter

```auto
[{"id":"960cbfbbef2d69c6","type":"inject","z":"2f5ea886d00cd91e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":110,"y":175,"wires":[["100cb4654a40c9fd","6e78c632028d6c8f"]]},{"id":"100cb4654a40c9fd","type":"api-current-state","z":"2f5ea886d00cd91e","name":"getal1","server":"3c6b2d2d.b63e72","version":3,"outputs":1,"halt_if":"","halt_if_type":"num","halt_if_compare":"is","entity_id":"input_number.getal1","state_type":"num","blockInputOverrides":false,"outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"entityState"},{"property":"data","propertyType":"msg","value":"","valueType":"entity"},{"property":"topic","propertyType":"msg","value":"node1","valueType":"str"}],"for":"0","forType":"num","forUnits":"minutes","override_topic":false,"state_location":"payload","override_payload":"msg","entity_location":"data","override_data":"msg","x":270,"y":150,"wires":[["0f2e0c0827bc1986"]]},{"id":"6e78c632028d6c8f","type":"api-current-state","z":"2f5ea886d00cd91e","name":"getal2","server":"3c6b2d2d.b63e72","version":3,"outputs":1,"halt_if":"","halt_if_type":"num","halt_if_compare":"is","entity_id":"input_number.getal1","state_type":"num","blockInputOverrides":false,"outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"entityState"},{"property":"data","propertyType":"msg","value":"","valueType":"entity"},{"property":"topic","propertyType":"msg","value":"node2","valueType":"str"}],"for":"0","forType":"num","forUnits":"minutes","override_topic":false,"state_location":"payload","override_payload":"msg","entity_location":"data","override_data":"msg","x":270,"y":200,"wires":[["0f2e0c0827bc1986"]]},{"id":"0f2e0c0827bc1986","type":"function","z":"2f5ea886d00cd91e","name":"c = context.node2 + context.node1","func":"context.node1 = context.node1 || 0;\ncontext.node2 = context.node2 || 0;\n\nif(msg.topic == 'node1'){\n context.node1 = msg.payload;\n} else if (msg.topic == 'node2') {\n context.node2 = msg.payload; \n}\n\nvar c = context.node2 + context.node1;\n\n\nreturn c;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":540,"y":175,"wires":[["68cd5c749e374caf"]]},{"id":"68cd5c749e374caf","type":"debug","z":"2f5ea886d00cd91e","name":"debug 358","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":795,"y":175,"wires":[]},{"id":"3c6b2d2d.b63e72","type":"server","name":"Home Assistant","version":5,"addon":true,"rejectUnauthorizedCerts":true,"ha_boolean":"y|yes|true|on|home|open","connectionDelay":true,"cacheJson":true,"heartbeat":false,"heartbeatInterval":30,"areaSelector":"friendlyName","deviceSelector":"friendlyName","entitySelector":"friendlyName","statusSeparator":"at: ","statusYear":"hidden","statusMonth":"short","statusDay":"numeric","statusHourCycle":"h23","statusTimeFormat":"h:m","enableGlobalContextStore":true}]

```

---

<div class="post-metadata">

**Author:** ![bakman2](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bakman2/32/6207_2.png) [@bakman2](https://discourse.nodered.org/u/bakman2)\
**Post date:** [17 March 2023 06:24 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/2 "2023-03-17T06:24:56Z")

</div>

Your flow does not work when imported. Export your flow again and follow these steps:

In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote `````)

````auto
``` 
   code goes here 
```

````

You can edit and correct your post by clicking the pencil ✏ icon.

See this post for more details - [How to share code or flow json](https://discourse.nodered.org/t/how-to-share-code-or-flow-json/506)

---

<div class="post-metadata">

**Author:** ![kroonp](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kroonp/32/68249_2.png) [@kroonp](https://discourse.nodered.org/u/kroonp)\
**Post date:** [17 March 2023 06:29 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/3 "2023-03-17T06:29:16Z")

</div>

```auto
[{"id":"960cbfbbef2d69c6","type":"inject","z":"2f5ea886d00cd91e","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"","payloadType":"date","x":110,"y":175,"wires":[["100cb4654a40c9fd","6e78c632028d6c8f"]]},{"id":"100cb4654a40c9fd","type":"api-current-state","z":"2f5ea886d00cd91e","name":"getal1","server":"3c6b2d2d.b63e72","version":3,"outputs":1,"halt_if":"","halt_if_type":"num","halt_if_compare":"is","entity_id":"input_number.getal1","state_type":"num","blockInputOverrides":false,"outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"entityState"},{"property":"data","propertyType":"msg","value":"","valueType":"entity"},{"property":"topic","propertyType":"msg","value":"node1","valueType":"str"}],"for":"0","forType":"num","forUnits":"minutes","override_topic":false,"state_location":"payload","override_payload":"msg","entity_location":"data","override_data":"msg","x":270,"y":150,"wires":[["0f2e0c0827bc1986"]]},{"id":"6e78c632028d6c8f","type":"api-current-state","z":"2f5ea886d00cd91e","name":"getal2","server":"3c6b2d2d.b63e72","version":3,"outputs":1,"halt_if":"","halt_if_type":"num","halt_if_compare":"is","entity_id":"input_number.getal1","state_type":"num","blockInputOverrides":false,"outputProperties":[{"property":"payload","propertyType":"msg","value":"","valueType":"entityState"},{"property":"data","propertyType":"msg","value":"","valueType":"entity"},{"property":"topic","propertyType":"msg","value":"node2","valueType":"str"}],"for":"0","forType":"num","forUnits":"minutes","override_topic":false,"state_location":"payload","override_payload":"msg","entity_location":"data","override_data":"msg","x":270,"y":200,"wires":[["0f2e0c0827bc1986"]]},{"id":"0f2e0c0827bc1986","type":"function","z":"2f5ea886d00cd91e","name":"c = context.node2 + context.node1","func":"context.node1 = context.node1 || 0;\ncontext.node2 = context.node2 || 0;\n\nif(msg.topic == 'node1'){\n context.node1 = msg.payload;\n} else if (msg.topic == 'node2') {\n context.node2 = msg.payload; \n}\n\nvar c = context.node2 + context.node1;\n\n\nreturn c;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":540,"y":175,"wires":[["68cd5c749e374caf"]]},{"id":"68cd5c749e374caf","type":"debug","z":"2f5ea886d00cd91e","name":"debug 358","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":795,"y":175,"wires":[]},{"id":"3c6b2d2d.b63e72","type":"server","name":"Home Assistant","version":5,"addon":true,"rejectUnauthorizedCerts":true,"ha_boolean":"y|yes|true|on|home|open","connectionDelay":true,"cacheJson":true,"heartbeat":false,"heartbeatInterval":30,"areaSelector":"friendlyName","deviceSelector":"friendlyName","entitySelector":"friendlyName","statusSeparator":"at: ","statusYear":"hidden","statusMonth":"short","statusDay":"numeric","statusHourCycle":"h23","statusTimeFormat":"h:m","enableGlobalContextStore":true}]

```

---

<div class="post-metadata">

**Author:** ![bakman2](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/bakman2/32/6207_2.png) [@bakman2](https://discourse.nodered.org/u/bakman2)\
**Post date:** [17 March 2023 06:43 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/4 "2023-03-17T06:43:40Z")

</div>

This is not how `context` works. See [documentation](https://nodered.org/docs/user-guide/writing-functions#storing-data).

But if you are always expecting 2 messages from 2 different topics, it is probably easier to use a join node instead, which can combine the 2 topics into a single message (note that this is based on the assumption that you actually always receive 2 messages)

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/9/b/9bae18eb5d020fbbde80b589bbffff4e4ce9273c.png)

---

<div class="post-metadata">

**Author:** ![cameo69](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/cameo69/32/66593_2.png) [@cameo69](https://discourse.nodered.org/u/cameo69)\
**Post date:** [17 March 2023 08:53 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/5 "2023-03-17T08:53:43Z")

</div>

I think your function returns wrongly.  
Try this function:

```auto
context.node1 = context.node1 || 0;
context.node2 = context.node2 || 0;

if(msg.topic == 'node1'){
    context.node1 = msg.payload;
} else if (msg.topic == 'node2') {
    context.node2 = msg.payload; 
}

var c = context.node2 + context.node1;

msg.payload = c;
return msg;

```

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/3/e/3e72370f7fb745cbd7e64fce8475e377219ae2be.png)

```auto
[{"id":"b0063c51cdfd417c","type":"inject","z":"c05fa2617ddabfc3","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"node1","payload":"3","payloadType":"num","x":420,"y":620,"wires":[["468bb01e6757aed8"]]},{"id":"468bb01e6757aed8","type":"function","z":"c05fa2617ddabfc3","name":"c = context.node2 + context.node1","func":"context.node1 = context.node1 || 0;\ncontext.node2 = context.node2 || 0;\n\nif(msg.topic == 'node1'){\n context.node1 = msg.payload;\n} else if (msg.topic == 'node2') {\n context.node2 = msg.payload; \n}\n\nvar c = context.node2 + context.node1;\n\nmsg.payload = c;\nreturn msg;","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":750,"y":640,"wires":[["70aacb57b866c708"]]},{"id":"70aacb57b866c708","type":"debug","z":"c05fa2617ddabfc3","name":"debug 359","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":1005,"y":640,"wires":[]},{"id":"5448bdfdc7fea366","type":"inject","z":"c05fa2617ddabfc3","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"node2","payload":"5","payloadType":"num","x":420,"y":660,"wires":[["468bb01e6757aed8"]]}]

```

Caveat: It will return for every incoming messages, regardless if node1 or node2 were sent ever.

---

<div class="post-metadata">

**Author:** ![kroonp](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kroonp/32/68249_2.png) [@kroonp](https://discourse.nodered.org/u/kroonp)\
**Post date:** [18 March 2023 07:42 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/6 "2023-03-18T07:42:35Z")

</div>

Thanx for you reply. Your code is working fine. It helped me a lot.  
👍

---

<div class="post-metadata">

**Author:** ![kroonp](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/kroonp/32/68249_2.png) [@kroonp](https://discourse.nodered.org/u/kroonp)\
**Post date:** [18 March 2023 07:44 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/7 "2023-03-18T07:44:29Z")

</div>

Your option with the join option is also working fine. Thankx  
👍

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [17 May 2023 07:44 UTC](https://discourse.nodered.org/t/sum-2-nodes-in-a-function/76648/8 "2023-05-17T07:44:58Z")

</div>

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