node red function add and remove object from context array - arrays

Question

I have a for loop in the node red function that a the start of the function I get the array from the context
var alarmArray = flow.get("alarmArray")
and after I need to push object on the array I have do this but I'm not pusching on the flow context array but in the local array
alarmArray.push({
key: "Low air pressure",
value: alarm1Cip
});
flow.set("alarm1CipOld",alarm1Cip);
and after in the for loop I need to remove the object from the context but in my way I remove it from local array
for (var key in alarmArray){
node.warn(key);
msg.payload = {
"title": alarmArray[key].key,
"isActive":alarmArray[key].value
};
node.send(msg)
delete alarmArray[key]
}
how can I manage to add and remove object in the context array?
thanks

Answer 1

The problem here is that NodeJS is a pass by reference language. This means that there are not 2 arrays here, only 1 that has 2 handles (var alarmArray and flow.get('alarmArray'))
This means that anything pushed/deleted on the "local" copy is also getting pushed/deleted to the copy in the context.
The only way to do what you want will be to make a deep copy of the array every time you recover it from the context and then work on the copy locally.
Assuming the array only holds simple objects then the following should work:
var alarmArray = JSON.parse(JSON.stringify(flow.get('alarmArray')))

Answer 2

If you want to save your changes you just have to reload the mutated object in the right context, overwriting the previous value with
flow.set('alarmArray', alarmArray)

Answer 3

You might better to use global.set instead of flow.set
This might help you.
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