# Help with context data

**URL:** <https://discourse.nodered.org/t/help-with-context-data/100468>\
**Category:** General\
**Tags:** dashboard-2\
**Created:** [27 February 2026 23:28 UTC](https://discourse.nodered.org/t/help-with-context-data/100468 "2026-02-27T23:28:19Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![montyfert](https://avatars.discourse-cdn.com/v4/letter/m/54ee81/32.png) [@montyfert](https://discourse.nodered.org/u/montyfert)\
**Post date:** [27 February 2026 23:28 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/1 "2026-02-27T23:28:19Z")

</div>

hi  
I'm trying to figure out context store , I've read the docs and watched to video but don't understand any of it . 😱  
I've managed to change the js file thingy to

contextStorage: {  
default: {  
module:"localfilesystem"  
},  
},  
and restarted node red, is there anything else i have to do ?  
here is my chart flow

```auto
[{"id":"5fd99dd03d10f4a1","type":"tab","label":"new daily high/low","disabled":false,"info":"","env":[]},{"id":"b40f8bf37be7f2e3","type":"group","z":"5fd99dd03d10f4a1","style":{"stroke":"#999999","stroke-opacity":"1","fill":"none","fill-opacity":"1","label":true,"label-position":"nw","color":"#a4a4a4"},"nodes":["9a8e6fed441c2029","4adc3c0e52c64503","2bfd8488040e2b7e","92c301603ab079c2","3f346011cacd22ca","cf1f054e8484dfbc","8611a498ddeac1fc","6d97f9a67c7bb40b","94146c0df761d3e5","f0267c8bebc47f17","1bf4760a84134919","8a863d12861905bd","2bc58a155b1d4d84","96593419eb4ceb39","ac960bd9f783d609","79ed2f986274d790","26f285d907cdc405","73a1c8201bdeb09b","9476cf9ce6f94391"],"x":14,"y":19,"w":772,"h":307},{"id":"79ed2f986274d790","type":"junction","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","x":160,"y":100,"wires":[["3f346011cacd22ca","cf1f054e8484dfbc"]]},{"id":"26f285d907cdc405","type":"junction","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","x":380,"y":100,"wires":[["8611a498ddeac1fc","6d97f9a67c7bb40b"]]},{"id":"73a1c8201bdeb09b","type":"junction","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","x":340,"y":300,"wires":[["1bf4760a84134919","8a863d12861905bd"]]},{"id":"9476cf9ce6f94391","type":"junction","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","x":760,"y":180,"wires":[["96593419eb4ceb39","ac960bd9f783d609"]]},{"id":"9a8e6fed441c2029","type":"function","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"function 21","func":"// Look in On Start\nlet msg1 = {}\nlet msg2 = {}\nlet msg3 = {}\nlet old = context.get('Day')\nlet day = new Date().getDay()\n\nif (old != day) {\n context.set('Day', day)\n context.set(\"Max\", -100)\n context.set(\"Min\", 100)\n}\n\nlet max = context.get('Max')\nlet min = context.get('Min')\n\nconst Tmp = msg.payload\n\nif (Tmp > max) {\n max = Tmp\n context.set('Max', Tmp)\n}\n\nif (Tmp < min) {\n min = Tmp\n context.set('Min', Tmp)\n}\n\nmsg1.payload = Tmp\nmsg1.topic = 'Tmp'\nmsg2.payload = max\nmsg2.topic = 'Max'\nmsg3.payload = min\nmsg3.topic = 'Min'\nreturn [msg1, msg2, msg3]\n","outputs":3,"timeout":0,"noerr":0,"initialize":"// Code added here will be run once\n// whenever the node is started.\n\ncontext.set(\"Day\", -1)\n ","finalize":"","libs":[],"x":270,"y":180,"wires":[["79ed2f986274d790"],["26f285d907cdc405","2bfd8488040e2b7e"],["92c301603ab079c2","73a1c8201bdeb09b"]]},{"id":"4adc3c0e52c64503","type":"mqtt in","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"Temperature","topic":"zone0/text","qos":"2","datatype":"auto-detect","broker":"b8758158381423f0","nl":false,"rap":true,"rh":0,"inputs":0,"x":110,"y":180,"wires":[["9a8e6fed441c2029"]]},{"id":"2bfd8488040e2b7e","type":"bar-chart-data2","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"bar-chart-data2","x_interval":"days","x_size":24,"unit":"","precision":"3","is_meter_reading":"False","agg_by":"max","x":480,"y":160,"wires":[["f0267c8bebc47f17"]]},{"id":"92c301603ab079c2","type":"bar-chart-data2","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"bar-chart-data2","x_interval":"days","x_size":24,"unit":"","precision":"3","is_meter_reading":"False","agg_by":"min","x":480,"y":200,"wires":[["f0267c8bebc47f17"]]},{"id":"3f346011cacd22ca","type":"ui_text","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","group":"e2740f14149858bd","order":1,"width":"18","height":1,"name":"","label":"Today's Temp","format":"{{msg.payload}}","layout":"row-spread","className":"","style":false,"font":"","fontSize":16,"color":"#000000","x":280,"y":80,"wires":[]},{"id":"cf1f054e8484dfbc","type":"debug","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"tmp","active":false,"tosidebar":false,"console":false,"tostatus":true,"complete":"true","targetType":"full","statusVal":"payload","statusType":"auto","x":250,"y":120,"wires":[]},{"id":"8611a498ddeac1fc","type":"ui_text","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","group":"e2740f14149858bd","order":3,"width":"18","height":1,"name":"","label":"Today's Max","format":"{{msg.payload}}","layout":"row-spread","className":"","style":false,"font":"","fontSize":16,"color":"#000000","x":490,"y":80,"wires":[]},{"id":"6d97f9a67c7bb40b","type":"debug","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"max","active":false,"tosidebar":false,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":470,"y":120,"wires":[]},{"id":"94146c0df761d3e5","type":"inject","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"clear","payloadType":"str","x":250,"y":240,"wires":[["2bfd8488040e2b7e","92c301603ab079c2"]]},{"id":"f0267c8bebc47f17","type":"function","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"","func":"let msg1 = {}\nlet invar = msg.payload\n\nif (msg.topics == undefined) { return }\nlet topic = msg.topics[0]\n\ncontext.data = context.data ?? {}\n\nswitch (topic) {\n case 'Max':\n context.data.max = invar\n break\n \n case 'Min':\n context.data.min = invar\n break\n}\n\nlet max = {}\nlet min = {}\nlet mm = {}\n\nif (context.data.max != null && context.data.min != null) {\n\n max.labels = context.data.max[0].labels\n max.series = [context.data.max[0].series[0]]\n max.data = [context.data.max[0].data[0]]\n\n min.labels = context.data.min[0].labels\n min.series = [context.data.min[0].series[0]]\n min.data = [context.data.min[0].data[0]]\n\n mm.labels = min.labels\n mm.series = [max.series[0], min.series[0]]\n mm.data = [max.data[0], min.data[0]]\n \n msg1.payload = [mm]\n return msg1\n}\n","outputs":1,"timeout":"","noerr":0,"initialize":"","finalize":"","libs":[],"x":640,"y":180,"wires":[["9476cf9ce6f94391"]]},{"id":"1bf4760a84134919","type":"debug","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"min","active":false,"tosidebar":false,"console":false,"tostatus":true,"complete":"payload","targetType":"msg","statusVal":"payload","statusType":"auto","x":430,"y":280,"wires":[]},{"id":"8a863d12861905bd","type":"ui_text","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","group":"e2740f14149858bd","order":5,"width":"18","height":1,"name":"","label":"Today's Min","format":"{{msg.payload}}","layout":"row-spread","className":"","style":false,"font":"","fontSize":16,"color":"#000000","x":450,"y":240,"wires":[]},{"id":"2bc58a155b1d4d84","type":"ui_button","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"","group":"e2740f14149858bd","order":8,"width":"18","height":"1","passthru":false,"label":"Clear All","tooltip":"","color":"","bgcolor":"","className":"","icon":"","payload":"[]","payloadType":"json","topic":"","topicType":"str","x":640,"y":220,"wires":[["9476cf9ce6f94391"]]},{"id":"96593419eb4ceb39","type":"ui_chart","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"","group":"e2740f14149858bd","order":7,"width":"18","height":"5","label":"","chartType":"bar","legend":"false","xformat":"HH:mm:ss","interpolate":"linear","nodata":"","dot":false,"ymin":"","ymax":"","removeOlder":"30","removeOlderPoints":"","removeOlderUnit":"60","cutout":0,"useOneColor":false,"useUTC":false,"colors":["#1f77b4","#aec7e8","#ff7f0e","#2ca02c","#98df8a","#d62728","#ff9896","#9467bd","#c5b0d5"],"outputs":1,"useDifferentColor":false,"className":"","x":630,"y":120,"wires":[[]]},{"id":"ac960bd9f783d609","type":"debug","z":"5fd99dd03d10f4a1","g":"b40f8bf37be7f2e3","name":"debug 63","active":false,"tosidebar":true,"console":false,"tostatus":false,"complete":"true","targetType":"full","statusVal":"","statusType":"auto","x":660,"y":60,"wires":[]},{"id":"b8758158381423f0","type":"mqtt-broker","name":"Local Broker","broker":"localhost","port":1883,"clientid":"","autoConnect":true,"usetls":false,"protocolVersion":4,"keepalive":60,"cleansession":true,"autoUnsubscribe":true,"birthTopic":"","birthQos":"0","birthRetain":"false","birthPayload":"","birthMsg":{},"closeTopic":"","closeQos":"0","closeRetain":"false","closePayload":"","closeMsg":{},"willTopic":"","willQos":"0","willRetain":"false","willPayload":"","willMsg":{},"userProps":"","sessionExpiry":""},{"id":"e2740f14149858bd","type":"ui_group","name":"bar-chart","tab":"957fd14a.a1277","order":1,"disp":true,"width":24,"collapse":false,"className":""},{"id":"957fd14a.a1277","type":"ui_tab","name":"bar-chart","icon":"dashboard","disabled":false,"hidden":false},{"id":"fcf20927f72f182b","type":"global-config","env":[],"modules":{"node-red-contrib-dashboard-bar-chart-data2":"0.9.101","node-red-dashboard":"3.6.6"}}]

```

I just want my charts not to forget all the info when i update node red or something .  
any help would be great  
thanks  
martin

---

<div class="post-metadata">

**Author:** ![jbudd](https://avatars.discourse-cdn.com/v4/letter/j/5f8ce5/32.png) [@jbudd](https://discourse.nodered.org/u/jbudd)\
**Post date:** [27 February 2026 23:53 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/2 "2026-02-27T23:53:08Z")

</div>

In your first function node you have

```auto
let old = context.get('Day')
let day = new Date().getDay()

if (old != day) {
    context.set('Day', day)
    context.set("Max", -100)
    context.set("Min", 100)
}

let max = context.get('Max')
let min = context.get('Min')

```

This creates three discrete context variables `Day`, `Min` and `Max`.  
All seems good.

In your second function node this code

```auto
context.data = context.data ?? {}

switch (topic) {
  case 'Max':
    context.data.max = invar
  break
 
  case 'Min':
    context.data.min = invar
  break
}

```

seems to be attempting to refer to the same variables as properties of an object `data`.  
You are using different, invalid syntax in this second function.  
Also I think that context variable names are case sensitive.

---

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [28 February 2026 05:19 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/3 "2026-02-28T05:19:16Z")

</div>

Sorry, not trying to be pedantic.

_CONTEXT_ is a bit vague.

If you are using `context` in a `function` node, the second one won't see it.  
(Or am I wrong?)

You need `flow` context.  
I haven't looked at the code itself.

But just in passing thought that needs clarifying.

---

<div class="post-metadata">

**Author:** ![gregorius](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/gregorius/32/73816_2.png) [@gregorius](https://discourse.nodered.org/u/gregorius)\
**Post date:** [28 February 2026 11:22 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/4 "2026-02-28T11:22:19Z")

</div>

here's the documentation --\> [Writing Functions : Node-RED](https://nodered.org/docs/user-guide/writing-functions#context)

```auto
context

    context.get(..) : get a node-scoped context property
    context.set(..) : set a node-scoped context property
    context.keys(..) : return a list of all node-scoped context property keys
    context.flow : same as flow
    context.global : same as global

flow

    flow.get(..) : get a flow-scoped context property
    flow.set(..) : set a flow-scoped context property
    flow.keys(..) : return a list of all flow-scoped context property keys

global

    global.get(..) : get a global-scoped context property
    global.set(..) : set a global-scoped context property
    global.keys(..) : return a list of all global-scoped context property keys

```

---

<div class="post-metadata">

**Author:** ![montyfert](https://avatars.discourse-cdn.com/v4/letter/m/54ee81/32.png) [@montyfert](https://discourse.nodered.org/u/montyfert)\
**Post date:** [28 February 2026 15:19 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/5 "2026-02-28T15:19:50Z")

</div>

hi i just want my charts not to loose their data when node red is restarted ,  
this is what i meant by context,

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/3/c/3ccc0e92f6573c240fe212cccc9a2d9bf780dd30.png)

---

<div class="post-metadata">

**Author:** ![Trying\_to\_learn](https://sea2.discourse-cdn.com/flex026/user_avatar/discourse.nodered.org/trying_to_learn/32/28400_2.png) [@Trying\_to\_learn](https://discourse.nodered.org/u/Trying_to_learn)\
**Post date:** [28 February 2026 19:13 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/6 "2026-02-28T19:13:00Z")

</div>

Yes, but - as said - `context` is a bit vague.

There are three _types_.  
Nodal - only in that node  
Flow - accessible to all nodes in that flow  
Global - accessible to ALL nodes on ALL flows

Also - and again - I didn't load your code.  
But reading that one `function` node does _something_ and you want that available to _another_ `function` node, AND the `chart`: `context` is NOT exactly the right term.

@jbudd mentioned a bit of your code:

```auto
let old = context.get('Day')
let day = new Date().getDay()

if (old != day) {
    context.set('Day', day)
    context.set("Max", -100)
    context.set("Min", 100)
}

let max = context.get('Max')
let min = context.get('Min')

```

The code has CONTEXT.SET - which is fine in some cases.  
But I suspect NOT in yours.

You need FLOW.SET (excusing it being in capitols)

Then the other nodes will have access to that data too.

I've been wrong in the past and will be again. But I am sure this is the cause of a lot of your pain just now.

---

<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:** [29 May 2026 19:13 UTC](https://discourse.nodered.org/t/help-with-context-data/100468/7 "2026-05-29T19:13:06Z")

</div>

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