# How to check if an Reference in msg.payload exists?

**URL:** <https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506>\
**Category:** General\
**Created:** [27 November 2019 10:36 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506 "2019-11-27T10:36:22Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![UweG](https://avatars.discourse-cdn.com/v4/letter/u/e495f1/32.png) [@UweG](https://discourse.nodered.org/u/UweG)\
**Post date:** [27 November 2019 10:36 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506/1 "2019-11-27T10:36:23Z")

</div>

Sometimes i get following reference in msg.payload and sometimes not.

msg.payload.Test

How can i check in a function if the reference 'Test' in payload exists or not?

payload always exists but sometimes with 'Test' and sometimes without.

If not exists i get following Error.  
ReferenceError: references is not defined

I tried:  
"if (msg.payload.hasOwnProperty("Test")){do something}"

But i don't know if i used it correctly or it is the right commando.

Anybody an idea?  
Thanks in advise.  
UweG

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<div class="post-metadata">

**Author:** ![knolleary](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/knolleary/32/3_2.png) [@knolleary](https://discourse.nodered.org/u/knolleary)\
**Post date:** [27 November 2019 10:40 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506/2 "2019-11-27T10:40:37Z")

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There are a few ways to do it, and the one you've identified, the `hasOwnProperty` function, is certainly a way to be sure it exists.

```auto
if (msg.payload.hasOwnProperty("Test")){
  // do something
}

```

One thing to be careful of is this check only tests if there is a property called `Test`. The value of the property could still be `null` or otherwise blank. So depending on your scenario, you may want to also check the value of `Test` before using it.

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<div class="post-metadata">

**Author:** ![UweG](https://avatars.discourse-cdn.com/v4/letter/u/e495f1/32.png) [@UweG](https://discourse.nodered.org/u/UweG)\
**Post date:** [27 November 2019 10:55 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506/3 "2019-11-27T10:55:53Z")

</div>

Thank's for your quick help.  
It works fine for me.  
Greetings  
UweG

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<div class="post-metadata">

**Author:** ![warnert](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/warnert/32/108132_2.png) [@warnert](https://discourse.nodered.org/u/warnert)\
**Post date:** [22 December 2022 21:29 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506/4 "2022-12-22T21:29:09Z")

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I have this:

```auto
var obj = msg.payload[0];
var regen2;
if (msg.payload.hasOwnProperty("rs_neerslag")) {
    regen2 = obj["rs_neerslag"];
}
else{
    // not found...
    regen2 = 0;
}

```

and this is what comes into the function node (from mysql):

```auto
SELECT rs_neerslag FROM regensensor WHERE rs_ts >= "2022-12-01:00:00:00" AND rs_ts <= "2022-12-01:23:59:59" ORDER BY rs_ts ASC LIMIT 1; : msg.payload : array[1]
array[1]
0: object
rs_neerslag: "3521.7"

```

and the result is that regen2 = 0....  
I believe it used to work. Has it someting to do with the new version? (I recently upgraded to 3.0.2)

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<div class="post-metadata">

**Author:** ![Steve-Mcl](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/steve-mcl/32/4826_2.png) [@Steve-Mcl](https://discourse.nodered.org/u/Steve-Mcl)\
**Post date:** [22 December 2022 23:12 UTC](https://discourse.nodered.org/t/how-to-check-if-an-reference-in-msg-payload-exists/18506/5 "2022-12-22T23:12:34Z")

</div>

Your result is in element 0 of the array in payload. So that's where you need to test...

`if (msg.payload[0].hasOwnProperty("rs_neerslag")) {`

Or

`if (obj.hasOwnProperty("rs_neerslag")) {`

However you should probably check the payload is actually an array AND that it's length is \>= 1 before you try to access `payload[0]`