# Extract value from array based JSON

**URL:** <https://discourse.nodered.org/t/extract-value-from-array-based-json/46787>\
**Category:** General\
**Created:** [6 June 2021 21:42 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787 "2021-06-06T21:42:36Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![norb3](https://avatars.discourse-cdn.com/v4/letter/n/7ba0ec/32.png) [@norb3](https://discourse.nodered.org/u/norb3)\
**Post date:** [6 June 2021 21:42 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787/1 "2021-06-06T21:42:36Z")

</div>

Hi,  
I have an json payload where data is organised inside an array and I want to obtain a value from one of the positions. since it is inside an array I need to filter the position that I want using a predicate. But I didn't find a working solution for this.

I am sending an JSON example below. I was trying to use a change node with a path like msg.payload.consumption[measurementType="total-consumption"].wNow but it doesn't work.

Any suggestions on how this could be achived?

JSON:  
{

```
"consumption": [
    {
        "type": "eim",
        "activeCount": 1,
        "measurementType": "total-consumption",
        "readingTime": 1623014333,
        "wNow": 471.878,
        "whLifetime": 64459558.361,
        "varhLeadLifetime": 22337648.955,
        "varhLagLifetime": 12438387.289,
        "vahLifetime": 67290585.179,
        "rmsCurrent": 6.355,
        "rmsVoltage": 688.198,
        "reactPwr": -1234.527,
        "apprntPwr": 4373.194,
        "pwrFactor": 0.11,
        "whToday": 28270.361,
        "whLastSevenDays": 216088.361,
        "vahToday": 32730.179,
        "varhLeadToday": 13200.955,
        "varhLagToday": 7067.289
    },
    {
        "type": "eim",
        "activeCount": 1,
        "measurementType": "net-consumption",
        "readingTime": 1623014333,
        "wNow": 476.109,
        "whLifetime": 43014212.263,
        "varhLeadLifetime": 22337561.058,
        "varhLagLifetime": 6528732.71,
        "vahLifetime": 67290585.179,
        "rmsCurrent": 5.533,
        "rmsVoltage": 688.309,
        "reactPwr": -1073.666,
        "apprntPwr": 1267.139,
        "pwrFactor": 0.38,
        "whToday": 0,
        "whLastSevenDays": 0,
        "vahToday": 0,
        "varhLeadToday": 0,
        "varhLagToday": 0
}
]

```

}

Thanks in advance,  
Norberto

---

<div class="post-metadata">

**Author:** ![E1cid](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/e1cid/32/77971_2.png) [@E1cid](https://discourse.nodered.org/u/E1cid)\
**Post date:** [6 June 2021 21:55 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787/2 "2021-06-06T21:55:22Z")

</div>

You need to select JSONata expression

```auto
[{"id":"5bae521e.35b5dc","type":"inject","z":"c74669a0.6a34f8","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"{\"consumption\": [{ \"type\": \"eim\", \"activeCount\": 1, \"measurementType\": \"total-consumption\", \"readingTime\": 1623014333, \"wNow\": 471.878, \"whLifetime\": 64459558.361, \"varhLeadLifetime\": 22337648.955, \"varhLagLifetime\": 12438387.289, \"vahLifetime\": 67290585.179, \"rmsCurrent\": 6.355, \"rmsVoltage\": 688.198, \"reactPwr\": -1234.527, \"apprntPwr\": 4373.194, \"pwrFactor\": 0.11, \"whToday\": 28270.361, \"whLastSevenDays\": 216088.361, \"vahToday\": 32730.179, \"varhLeadToday\": 13200.955, \"varhLagToday\": 7067.289 }, { \"type\": \"eim\", \"activeCount\": 1, \"measurementType\": \"net-consumption\", \"readingTime\": 1623014333, \"wNow\": 476.109, \"whLifetime\": 43014212.263, \"varhLeadLifetime\": 22337561.058, \"varhLagLifetime\": 6528732.71, \"vahLifetime\": 67290585.179, \"rmsCurrent\": 5.533, \"rmsVoltage\": 688.309, \"reactPwr\": -1073.666, \"apprntPwr\": 1267.139, \"pwrFactor\": 0.38, \"whToday\": 0, \"whLastSevenDays\": 0, \"vahToday\": 0, \"varhLeadToday\": 0, \"varhLagToday\": 0 }]}","payloadType":"json","x":120,"y":2260,"wires":[["cce946dc.3de4b8"]]},{"id":"cce946dc.3de4b8","type":"change","z":"c74669a0.6a34f8","name":"","rules":[{"t":"set","p":"payload","pt":"msg","to":"payload.consumption[measurementType=\"total-consumption\"].wNow","tot":"jsonata"}],"action":"","property":"","from":"","to":"","reg":false,"x":340,"y":2260,"wires":[["404ab792.b606f"]]},{"id":"404ab792.b606f","type":"debug","z":"c74669a0.6a34f8","name":"","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"false","statusVal":"","statusType":"auto","x":580,"y":2280,"wires":[]}]

```

Here is an example

---

<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:** [6 June 2021 21:55 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787/3 "2021-06-06T21:55:55Z")

</div>

In a function node...

```auto
var x = msg.payload.consumption.find(e=>e.measurementType=="total-consumption");
msg.payload = x;

```

---

<div class="post-metadata">

**Author:** ![norb3](https://avatars.discourse-cdn.com/v4/letter/n/7ba0ec/32.png) [@norb3](https://discourse.nodered.org/u/norb3)\
**Post date:** [7 June 2021 18:37 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787/4 "2021-06-07T18:37:32Z")

</div>

Thanks for your help guys.  
I have ended up doing the function.  
Norberto

---

<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:** [21 June 2021 18:37 UTC](https://discourse.nodered.org/t/extract-value-from-array-based-json/46787/5 "2021-06-21T18:37:33Z")

</div>

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