# Function Node with RBE functionality, issue with JSON Objects

**URL:** <https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854>\
**Category:** General\
**Created:** [8 December 2021 06:28 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854 "2021-12-08T06:28:36Z")\
**Posts on this page:** 10\
**Page:** 1

<div class="post-metadata">

**Author:** ![GeorgeCastanza](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/georgecastanza/32/40766_2.png) [@GeorgeCastanza](https://discourse.nodered.org/u/GeorgeCastanza)\
**Post date:** [8 December 2021 06:28 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/1 "2021-12-08T06:28:36Z")

</div>

Hey, I know I could do this with the RBE/filter node, but it's in some code, and I'd like to keep it in the function node.

Is there a way for this code to check for JSON objects. It does check for numbers/strings etc. But JSON objects seems to get through the code even if it's identical.  
This is the code in the function node.

```auto
// block unless value changes

var new_input = msg.payload;
var last_output = context.get("last_output");
var master = global.get("master_office_lights");

if (master == "off"){
    if (typeof last_output == 'undefined') {
        context.set("last_output", new_input);
        return msg; // forward initial value
        // * return null to ignore the initial value * //
    }
    
    // otherwise last_output is defined, so did it change?
    if (new_input == last_output) {
        return null;
    }
    else {
        context.set("last_output", new_input);
        return msg;
    }
}

if (master =="on"){
    context.set("last_output", 'cleared')
    }

```

Here is a flow that shows an object it gets through the function node, but is stopped by the RBE node.

```auto
[{"id":"e221f25fc838887b","type":"function","z":"8c249630.076968","name":"RBE & Gate","func":"// block unless value changes\n\nvar new_input = msg.payload;\nvar last_output = context.get(\"last_output\");\nvar master = global.get(\"master_office_lights\");\n\nif (master == \"off\"){\n if (typeof last_output == 'undefined') {\n context.set(\"last_output\", new_input);\n return msg; // forward initial value\n // * return null to ignore the initial value * //\n }\n \n // otherwise last_output is defined, so did it change?\n if (new_input == last_output) {\n return null;\n }\n else {\n context.set(\"last_output\", new_input);\n return msg;\n }\n}\n\nif (master ==\"on\"){\n context.set(\"last_output\", 'cleared')\n }","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":670,"y":1600,"wires":[["6c25fc06b3647bd6"]]},{"id":"6c25fc06b3647bd6","type":"debug","z":"8c249630.076968","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":850,"y":1600,"wires":[]},{"id":"cf463ab38a1e0c24","type":"inject","z":"8c249630.076968","name":"","props":[{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":310,"y":1560,"wires":[["1f77d8bf169d02dd"]]},{"id":"538f59be7e060990","type":"inject","z":"8c249630.076968","name":"","props":[{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","x":310,"y":1600,"wires":[["e25aa489742d569d"]]},{"id":"91e9fdaa2d1b1d30","type":"inject","z":"8c249630.076968","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"-13","payloadType":"num","x":310,"y":1660,"wires":[["e221f25fc838887b","b67a2e571f2eff2c"]]},{"id":"1f77d8bf169d02dd","type":"function","z":"8c249630.076968","name":"","func":"return {payload:{data:{'brightness_pct':60,'color_temp':275}}}","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":470,"y":1560,"wires":[["e221f25fc838887b","b67a2e571f2eff2c"]]},{"id":"e25aa489742d569d","type":"function","z":"8c249630.076968","name":"","func":"return {payload:{\"service\": \"turn_off\" }}","outputs":1,"noerr":0,"initialize":"","finalize":"","libs":[],"x":460,"y":1600,"wires":[["e221f25fc838887b","b67a2e571f2eff2c"]]},{"id":"b67a2e571f2eff2c","type":"rbe","z":"8c249630.076968","name":"","func":"rbe","gap":"","start":"","inout":"out","septopics":false,"property":"payload","topi":"topic","x":675,"y":1660,"wires":[["3850a39194311ea6"]],"l":false},{"id":"3850a39194311ea6","type":"debug","z":"8c249630.076968","name":"","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":850,"y":1660,"wires":[]}]

```

---

<div class="post-metadata">

**Author:** ![Colin](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/colin/32/17040_2.png) [@Colin](https://discourse.nodered.org/u/Colin)\
**Post date:** [8 December 2021 08:57 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/2 "2021-12-08T08:57:13Z")

</div>

You can't compare the contents of objects in javascript using `==`.

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [8 December 2021 09:03 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/3 "2021-12-08T09:03:04Z")

</div>

Try googling 'javascript how to check for an object'

---

<div class="post-metadata">

**Author:** ![GeorgeCastanza](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/georgecastanza/32/40766_2.png) [@GeorgeCastanza](https://discourse.nodered.org/u/GeorgeCastanza)\
**Post date:** [8 December 2021 22:09 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/4 "2021-12-08T22:09:04Z")

</div>

Yeah, I tried, but beyond my paygrade. Any particular page to look at?

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [9 December 2021 00:13 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/5 "2021-12-09T00:13:03Z")

</div>

> [@zenofmud](#):
>
> javascript how to check for an object'

What site did you look at and what didn’t you understand?

---

<div class="post-metadata">

**Author:** ![Buckskin](https://avatars.discourse-cdn.com/v4/letter/b/b9e5f3/32.png) [@Buckskin](https://discourse.nodered.org/u/Buckskin)\
**Post date:** [9 December 2021 00:37 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/6 "2021-12-09T00:37:59Z")

</div>

I know that this is short circuiting the teaching/learning process but this is one way (look for [Stackoverflow](https://stackoverflow.com) as a source of answers;

This is one way

```auto
/**

    * Description Determines whether or not supplied argument is of type 'object'.
    * 
    * @param {*} objValue - The argument to check.
    * 
    * @return {boolean} - True if the argument is of type 'object', otherwise false.
    */

    function isObject(objValue) {

        return objValue != null && objValue.constructor.name === 'Object';

    } // End Function isObject()

```

---

<div class="post-metadata">

**Author:** ![GeorgeCastanza](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/georgecastanza/32/40766_2.png) [@GeorgeCastanza](https://discourse.nodered.org/u/GeorgeCastanza)\
**Post date:** [9 December 2021 03:34 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/7 "2021-12-09T03:34:37Z")

</div>

> [@zenofmud](#):
>
> javascript how to check for an object

> <https://stackoverflow.com/questions/8511281/check-if-a-value-is-an-object-in-javascript>

> <https://stackoverflow.com/questions/27509/detecting-an-undefined-object-property>

> **[How to Check if a Value is an Object in JavaScript](https://www.w3docs.com/snippets/javascript/how-to-check-if-a-value-is-an-object-in-javascript.html)**
>
> Checking the data type of the value can be misleading. Read this tutorial and learn which operator is used to check if a value is an object in JavaScript.

> **[3 Ways to Check If an Object Has a Property/Key in JavaScript](https://dmitripavlutin.com/check-if-object-has-property-javascript/)**
>
> The 3 ways to check if an object has a property or key in JavaScript: hasOwnProperty() method, in operator, comparing with undefined.

> **[Check if a variable is a JavaScript object.](https://thisinterestsme.com/check-variable-javascript-object/)**
>
> This is a short guide on how to check if a variable or value if an object using JavaScript.

> **[How to Check for an Object in Javascript (Object Null Check)](https://levelup.gitconnected.com/how-to-check-for-an-object-in-javascript-object-null-check-3b2632330296)**
>
> When you check for an object in JavaScript, you also need to include a null check, because the typeof null is "object".

My issue is, I dont know why it's not working. I'm no coder, obviously. Just a tinkerer. I'm not sure if it's because it's undefined, or because it was missing the === I learn by seeing what someone else has done, and working from that. Thanks @Buckskin, I'll take a look at that page.

---

<div class="post-metadata">

**Author:** ![GeorgeCastanza](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/georgecastanza/32/40766_2.png) [@GeorgeCastanza](https://discourse.nodered.org/u/GeorgeCastanza)\
**Post date:** [9 December 2021 03:54 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/8 "2021-12-09T03:54:03Z")

</div>

So, I think I understand where I was going wrong. Please correct me if I'm wrong.

Since json does something weird, it results in "undefined" from typeof. Thus, in my code above, it always is passed through given the return msg. Is that correct?

---

<div class="post-metadata">

**Author:** ![zenofmud](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/zenofmud/32/316_2.png) [@zenofmud](https://discourse.nodered.org/u/zenofmud)\
**Post date:** [9 December 2021 09:18 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/9 "2021-12-09T09:18:59Z")

</div>

In your `function` 'RBE & Gate' the first time it is run neither the global or the contect variables will exist. This is explained in the Node-RED documentation: [Writing Functions : Node-RED](https://nodered.org/docs/user-guide/writing-functions#storing-data).

Since `global.get("master_office_lights")` will not return anything, both

> `if (master == "off")`

and

> `if (master == "on")`

will be false and nothing is done. And if you initialize the global prior to this function node, the context variable is not initialized.

In addition, you are injecting an object in msg.payload but if 'master' is 'on' you set the context variable to a string. A string will never equal an object so `new_input` will never equal `last_output`.

A great way to debug `function` nodes (see: [Writing Functions : Node-RED](https://nodered.org/docs/user-guide/writing-functions#logging-events)) is to use `node.warn(put something here)`. You could add `node.warn('debug 1')`  
`node.warn('debug 2')`  
etc... in different parts of the code to see what the path in your code is. You can also use variables in node.warn by using  
`node.warn("x =" + x)`  
however if `x` is an object you will get `x =[object Object]`. You can add two debug nodes  
`node.warn("x =")`  
`node.warn(x)`  
which will return two debug messages and you will be able to expand the object to see what it contains.

Hopefully this will help you move forward with your function by discovering the problems you have in your code. Feel free to ask for more help with your debugging.

p.s. here is a small flow to set the global variable on or off to help you test your code:

```auto
[{"id":"44cfe5b3000dc1a1","type":"inject","z":"bfb19c4d8b07d765","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"on","payloadType":"str","x":190,"y":340,"wires":[["f4be8b8ce82d935b"]]},{"id":"f4be8b8ce82d935b","type":"change","z":"bfb19c4d8b07d765","name":"","rules":[{"t":"set","p":"master_office_lights","pt":"global","to":"payload","tot":"msg"}],"action":"","property":"","from":"","to":"","reg":false,"x":470,"y":360,"wires":[[]]},{"id":"e672fefca2065ed8","type":"inject","z":"bfb19c4d8b07d765","name":"","props":[{"p":"payload"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"off","payloadType":"str","x":190,"y":400,"wires":[["f4be8b8ce82d935b"]]}]

```

---

<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:** [7 February 2022 09:19 UTC](https://discourse.nodered.org/t/function-node-with-rbe-functionality-issue-with-json-objects/54854/10 "2022-02-07T09:19:14Z")

</div>

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