# Dynamically editing URL message content using a function
**URL:** https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370
**Category:** General
**Tags:** http-request, function-node
**Created:** [13 February 2025 10:31 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370 "2025-02-13T10:31:30Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@shlomo](https://discourse.nodered.org/u/shlomo)
#### Post date: [13 February 2025 10:31 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/1 "2025-02-13T10:31:30Z")
Hello everyone, I have a flow that is supposed to send me a WhatsApp message via "CallMeBot" when there is an inequality between two nodes
But in practice I can't get it to work even though I checked the API KEY and it works, and the join node also outputs an array Something in the function doesn't work for me....
```auto
[
{
"id": "node1",
"type": "inject",
"z": "flow1",
"name": "Node 1 Value",
"props": [
{
"p": "payload",
"v": "{\"name\": \"Sensor A\", \"value\": 50}",
"vt": "json"
}
],
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"wires": [["joinNode"]]
},
{
"id": "node2",
"type": "inject",
"z": "flow1",
"name": "Node 2 Value",
"props": [
{
"p": "payload",
"v": "{\"name\": \"Sensor B\", \"value\": 40}",
"vt": "json"
}
],
"repeat": "",
"crontab": "",
"once": false,
"onceDelay": 0.1,
"wires": [["joinNode"]]
},
{
"id": "joinNode",
"type": "join",
"z": "flow1",
"name": "Join Sensor Data",
"mode": "custom",
"build": "array",
"property": "payload",
"propertyType": "msg",
"key": "topic",
"joiner": "\\n",
"timeout": "",
"count": "2",
"wires": [["functionNode"]]
},
{
"id": "functionNode",
"type": "function",
"z": "flow1",
"name": "Compare & Alert",
"func": "let node1 = msg.payload[0];\nlet node2 = msg.payload[1];\n\nlet node1Value = node1.value;\nlet node2Value = node2.value;\n\nlet node1Name = node1.name || \"Node 1\";\nlet node2Name = node2.name || \"Node 2\";\n\nlet currentDifference = Math.abs(node1Value - node2Value);\nlet threshold = 10;\nlet previousDifference = context.get(\"previousDifference\") || currentDifference;\nlet differenceChange = Math.abs(currentDifference - previousDifference);\n\nif (differenceChange >= threshold) {\n let alertMessage = `ā ļø Alert! Significant change detected!\\nš Node: ${node1Name} vs. ${node2Name}\\nš¢ Previous Difference: ${previousDifference}\\nš¢ Current Difference: ${currentDifference}\\nš Change: ${differenceChange}`;\n \n msg.payload = {\n url: \"https://api.callmebot.com/whatsapp.php?phone=+1234567890&text=\" + encodeURIComponent(alertMessage) + \"&apikey=YOUR_API_KEY\",\n method: \"GET\"\n };\n \n context.set(\"previousDifference\", currentDifference);\n return msg;\n}\nreturn null;",
"outputs": 1,
"noerr": 0,
"wires": [["httpRequestNode"]]
},
{
"id": "httpRequestNode",
"type": "http request",
"z": "flow1",
"name": "Send CallMeBot Alert",
"method": "GET",
"ret": "txt",
"paytoqs": "query",
"url": "",
"tls": "",
"persist": false,
"proxy": "",
"authType": "",
"x": 500,
"y": 200,
"wires": [["debugNode"]]
},
{
"id": "debugNode",
"type": "debug",
"z": "flow1",
"name": "Debug Response",
"active": true,
"tosidebar": true,
"console": false,
"tostatus": false,
"complete": "payload",
"targetType": "msg",
"x": 700,
"y": 200,
"wires": []
}
]
```
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [13 February 2025 10:57 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/2 "2025-02-13T10:57:24Z")
Hi, welcome to the forum,
In your function you send
```js
msg.payload = {
url: "https://api.callmebot.com/whatsapp.php?phone=+1234567890&text=" + encodeURIComponent(alertMessage) + "&apikey=YOUR_API_KEY",
method: "GET"
};
```
That is not correct. The built in help does not explicitly say that the inputs are or are not part of payload so I can understand your confusion but the answer is...
```auto
msg.url = "https://blah-blah",
msg.method = ... etc
msg.headers = ... etc
```
---
### Author:  [@shlomo](https://discourse.nodered.org/u/shlomo)
#### Post date: [13 February 2025 11:47 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/3 "2025-02-13T11:47:12Z")
Hi Stephen, thank you for your help. I made this correction, but it still doesn't solve my problem...
What bothers me is the fact that the debug node after the function doesn't output anything.
```auto
msg.url = "https://api.callmebot.com/whatsapp.php?phone=972587202215&text=" + encodeURIComponent(alertMessage) + "&apikey = 1201647" ,
msg.method = "GET",
```
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [13 February 2025 11:49 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/4 "2025-02-13T11:49:29Z")
> [@shlomo](#):
>
> the debug node after the function doesn't output anything.
did you delete the `return msg` from the end? Thats how the msg is passed to the next node.
[https://nodered.org/docs/user-guide/writing-functions](https://nodered.org/docs/user-guide/writing-functions)
---
### Author:  [@shlomo](https://discourse.nodered.org/u/shlomo)
#### Post date: [13 February 2025 12:12 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/5 "2025-02-13T12:12:11Z")
Now I see that the "return msg" was before the brackets
I fixed it, and now the Http node gives me a debug like this "No url specified"
Including the latest function
```auto
let node1 = msg.payload[0];
let node2 = msg.payload[1];
let node1Value = node1.value;
let node2Value = node2.value;
let node1Name = node1.name || "Node 1";
let node2Name = node2.name || "Node 2";
let currentDifference = Math.abs(node1Value - node2Value);
let threshold = 9;
let previousDifference = context.get("previousDifference") || currentDifference;
let differenceChange = Math.abs(currentDifference - previousDifference);
if (differenceChange >= threshold) {
let alertMessage = " Alert! Significant change detected!\n Node: ${node1Name} vs. ${node2Name}\n Previous Difference: ${previousDifference}\n Current Difference: ${currentDifference}\n Change: ${differenceChange}";
msg.url = "https://api.callmebot.com/whatsapp.php?phone=972587202215&text=" + encodeURIComponent(alertMessage) + "&apikey = 1201647" ,
msg.method = "GET",
context.set("previousDifference", currentDifference);
}
return msg;
```
---
### Author:  [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)
#### Post date: [13 February 2025 12:18 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/6 "2025-02-13T12:18:34Z")
> [@shlomo](#):
>
> and now the Http node gives me a debug like this "No url specified"
Did the debug contain `msg.url`? (you might need to set the debug to "Show complete Message"
At a guess, `differenceChange >= threshold` was NOT true.
Try adding debug statemenets to your code to understand why
```auto
node.warn({differenceChange, threshold})
if (differenceChange >= threshold) {
let alertMessage = " Alert! Significant change detected!\n Node: ${node1Name} vs. ${node2Name}\n Previous Difference: ${previousDifference}\n Current Difference: ${currentDifference}\n Change: ${differenceChange}";
msg.url = "https://api.callmebot.com/whatsapp.php?phone=972587202215&text=" + encodeURIComponent(alertMessage) + "&apikey = 1201647" ,
msg.method = "GET",
context.set("previousDifference", currentDifference);
} else {
node.warn("differenceChange is NOT >= threshold")
}
```
Lastly, you probably dont want to send the msg to the REQUEST if the URL is not set so move your `return` inside of the `if` OR use a `switch` node AFTER the function to check that `msg.url` is a string.
e.g.
```js
node.warn({differenceChange, threshold})
if (differenceChange >= threshold) {
let alertMessage = " Alert! Significant change detected!\n Node: ${node1Name} vs. ${node2Name}\n Previous Difference: ${previousDifference}\n Current Difference: ${currentDifference}\n Change: ${differenceChange}";
msg.url = "https://api.callmebot.com/whatsapp.php?phone=972587202215&text=" + encodeURIComponent(alertMessage) + "&apikey = 1201647" ,
msg.method = "GET",
context.set("previousDifference", currentDifference);
return msg // <<<<<< Return the msg - pass it to the next node
} else {
node.warn("differenceChange is NOT >= threshold")
return null // <<<<<< STOP THE FLOW - dont pass it to the next node
}
```
---
### Author:  [@jbudd](https://discourse.nodered.org/u/jbudd)
#### Post date: [13 February 2025 12:45 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/7 "2025-02-13T12:45:15Z")
> [@shlomo](#):
>
> ```auto
> let currentDifference = Math.abs(node1Value - node2Value);
> let threshold = 9;
> let previousDifference = context.get("previousDifference") || currentDifference;
> let differenceChange = Math.abs(currentDifference - previousDifference);
>
> if (differenceChange >= threshold) {
> let alertMessage = " Alert! Significant change detected!\n Node: ${node1Name} vs. ${node2Name}\n Previous Difference: ${previousDifference}\n Current Difference: ${currentDifference}\n Change: ${differenceChange}";
> msg.url = "https://api.callmebot.com/whatsapp.php?phone=972587202215&text=" + encodeURIComponent(alertMessage) + "&apikey = 1201647" ,
> msg.method = "GET",
> context.set("previousDifference", currentDifference);
> }
>
> ```
Just to point out that there's already a filter node to do precisely that - only pass on a message if a value differs enough from the previous value.
Not everything has to be coded in javascript š
---
### Author:  [@system](https://discourse.nodered.org/u/system)
#### Post date: [14 May 2025 12:46 UTC](https://discourse.nodered.org/t/dynamically-editing-url-message-content-using-a-function/95370/8 "2025-05-14T12:46:12Z")
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