# Strange behaviour of assign of context var with init bool value

**URL:** <https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026>\
**Category:** General\
**Created:** [15 March 2019 15:20 UTC](https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026 "2019-03-15T15:20:10Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Frank2](https://avatars.discourse-cdn.com/v4/letter/f/f9ae1b/32.png) [@Frank2](https://discourse.nodered.org/u/Frank2)\
**Post date:** [15 March 2019 15:20 UTC](https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026/1 "2019-03-15T15:20:10Z")

</div>

Does anyone see what i am doing wrong? After defining the variables with a context get it goes wel for all except for the bool one. SetTempCFirst is not set in the program and stays alwas true. If i put in the extra line SetTempCFirstOn = context.get('SetTempCFirstOn') everything works as expected.

SetTempC = context.get('SetTempC') || 0  
SetTempCOld = context.get('SetTempCOld') || 0  
SetTempCFirstOn = context.get('SetTempCFirstOn') || true

// Line below changes result. Otherwise SetTempCFirstOn is not set and always true  
SetTempCFirstOn = context.get('SetTempCFirstOn')  
if (msg.topic == 'SetTempC') {  
context.set('SetTempC',msg.payload)  
msg1 = null  
msg2 = null  
}

if (msg.topic == 'Tick') {  
if (msg.payload == 'on') {  
msg1 = {payload:SetTempC}  
msg1.topic = 'SetTempC'  
// Check if it's turned on  
if (SetTempCFirstOn === true) {  
msg2 = {payload:'ON'}  
msg2.topic = 'SetTempCTimer'  
context.set('SetTempCFirstOn',false)  
} else {  
// Check status changed  
if (SetTempCOld != SetTempC) {  
msg2 = {payload:'CHANGED'}  
msg2.topic = 'SetTempCTimer'  
context.set('SetTempCOld',SetTempC)  
} else {  
msg2 = null  
}  
}  
}  
if (msg.payload == 'stopped') {  
msg1 = null  
msg2 = {payload:'OFF'}  
msg2.topic = 'SetTempCTimer'  
context.set('SetTempCFirstOn',true)  
}  
}  
return [msg1, msg2];

```auto
[{"id":"e2ffd826.ee8d18","type":"tab","label":"Flow 2","disabled":false,"info":""},{"id":"34f9d7cb.0fe788","type":"looptimer","z":"e2ffd826.ee8d18","duration":"2","units":"Second","maxloops":"1000","maxtimeout":"1","maxtimeoutunits":"Hour","name":"","x":301,"y":144,"wires":[["9777f42a.08c978"],["9777f42a.08c978"]]},{"id":"9e31a61f.d361f8","type":"inject","z":"e2ffd826.ee8d18","name":"","topic":"Tick","payload":"on","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":89,"y":132,"wires":[["34f9d7cb.0fe788"]]},{"id":"a2c38919.dc6358","type":"inject","z":"e2ffd826.ee8d18","name":"","topic":"Tick","payload":"STOP","payloadType":"str","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":97,"y":172,"wires":[["34f9d7cb.0fe788"]]},{"id":"dcbb2173.3158c","type":"inject","z":"e2ffd826.ee8d18","name":"","topic":"SetTempC","payload":"100","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":117,"y":220,"wires":[["9777f42a.08c978"]]},{"id":"83237633.5e8d08","type":"inject","z":"e2ffd826.ee8d18","name":"","topic":"SetTempC","payload":"150","payloadType":"num","repeat":"","crontab":"","once":false,"onceDelay":0.1,"x":118,"y":268,"wires":[["9777f42a.08c978"]]},{"id":"9777f42a.08c978","type":"function","z":"e2ffd826.ee8d18","name":"TimeControl2","func":"SetTempC = context.get('SetTempC') || 0\nSetTempCOld = context.get('SetTempCOld') || 0\nSetTempCFirstOn = context.get('SetTempCFirstOn') || true\n\n// Line below changes result. Otherwise SetTempCFirstOn is not set and always true\nSetTempCFirstOn = context.get('SetTempCFirstOn')\nif (msg.topic == 'SetTempC') {\n context.set('SetTempC',msg.payload)\n msg1 = null\n msg2 = null\n}\n\nif (msg.topic == 'Tick') { \n if (msg.payload == 'on') {\n msg1 = {payload:SetTempC}\n msg1.topic = 'SetTempC'\n // Check if it's turned on\n if (SetTempCFirstOn === true) {\n msg2 = {payload:'ON'}\n msg2.topic = 'SetTempCTimer'\n context.set('SetTempCFirstOn',false)\n } else {\n // Check status changed\n if (SetTempCOld != SetTempC) {\n msg2 = {payload:'CHANGED'}\n msg2.topic = 'SetTempCTimer'\n context.set('SetTempCOld',SetTempC)\n } else {\n msg2 = null\n } \n } \n } \n if (msg.payload == 'stopped') {\n msg1 = null\n msg2 = {payload:'OFF'}\n msg2.topic = 'SetTempCTimer'\n context.set('SetTempCFirstOn',true)\n }\n}\nreturn [msg1, msg2];","outputs":2,"noerr":0,"x":537,"y":178,"wires":[["db71092d.2edfd8"],["1b251a56.40ad86"]]},{"id":"1b251a56.40ad86","type":"debug","z":"e2ffd826.ee8d18","name":"output 2","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":555,"y":314,"wires":},{"id":"db71092d.2edfd8","type":"debug","z":"e2ffd826.ee8d18","name":"output 1","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","x":609,"y":74,"wires":}]

```

---

<div class="post-metadata">

**Author:** ![Frank2](https://avatars.discourse-cdn.com/v4/letter/f/f9ae1b/32.png) [@Frank2](https://discourse.nodered.org/u/Frank2)\
**Post date:** [15 March 2019 15:23 UTC](https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026/2 "2019-03-15T15:23:59Z")

</div>

Solved: it's not assigning but a trick 😉 Use assign to be sure. Works only with non bool values.

---

<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:** [15 March 2019 15:26 UTC](https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026/3 "2019-03-15T15:26:59Z")

</div>

> [@Frank2](#):
>
> SetTempCFirstOn = context.get('SetTempCFirstOn') || true

The problem is the way you are trying to set the default value using the || operator.

If you set `SetTempCFirstOn` to `false` then the above code will return true because the left-hand side of the `||` is false.

If `false` is a valid value, then you cannot use the `||` trick - you have to be explicit:

```auto
var SetTempCFirstOn = context.get('SetTempCFirstOn');
if (SetTempCFirstOn === undefined) {
    SetTempCFirstOn = true
}

```

Please also read this post about how to share code/flows in the forum - [How to share code or flow json](https://discourse.nodered.org/t/how-to-share-code-or-flow-json/506)

---

<div class="post-metadata">

**Author:** ![Frank2](https://avatars.discourse-cdn.com/v4/letter/f/f9ae1b/32.png) [@Frank2](https://discourse.nodered.org/u/Frank2)\
**Post date:** [15 March 2019 17:04 UTC](https://discourse.nodered.org/t/strange-behaviour-of-assign-of-context-var-with-init-bool-value/9026/4 "2019-03-15T17:04:04Z")

</div>

Pfff that was a pain to find out. Thought I was gone crazy. I was presuming it was a valid stament to assign values but it is a trick when there is a false on the left side the right side is chosen. A pipe statement. That I have to find out by try and error.

Thanks without this explanation I scratched my head even longer.