Dynamic context scope for get function

General
1

Hello.

I'm trying to write a simple function which will validate if variable exist in the context store.
The function will accept two inputs: var_name and scope and return the value if the variable exists.

Is there any way to dynamically change the scope for get() function?
My code example is below:

getVar('Qty','global')
function getVar(var_name, scope) {
    node.warn('scope is: '+ scope)
    contextCall = [scope].get(var_name)
    if (typeof contextCall[var_name] != "undefined") {
        msg[var_name]=contextCall[var_name]
    } else {
        msg[var_name] = false;
        }
}
return msg;

PS. I know how to do it with eval, just wondering if there is another way.

const contextCall = {[`${var_name}`]:(eval(`${scope}.get(var_name)`))}
2

Dont use exec. There are helper functions built into node-red function node. These are immediately obvious if you use the monaco editor...
chrome_M77eu489af

On to your issue: here is a function that works...

const pl = msg.payload
msg.payload = {}
// hard coded tests ↓ delete these!
getVar('global', 'global1', msg, 'payload.hard_coded.dest_sub_prop.global1_value')
getVar('flow', 'flow1', msg, 'payload.hard_coded.dest_sub_prop.flow1_value')

//dynamic from msg props
getVar(pl.scope, pl.prop, msg, pl.msgProp)

function getVar(scope, var_name, msg, msgProp) {
    const contextscope = this[scope]
    if (!contextscope) {
        node.error(`bad scope: ${scope}`, msg);
        return null
    }
    const value = RED.util.cloneMessage(contextscope.get(var_name))
    if (msg) {
        msgProp = msgProp || var_name
        RED.util.setObjectProperty(msg, msgProp, value, true);
    }
    return value
}
return msg;

Here is a working demo demonstrating a few of the possibilities when using the node-red helpers...

image
image697Ă—523 39.2 KB 

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