How to append a custom object built from http request parameters to a global context array in node-red?

Question

In nodered I want to add a JSON object to an array stored in a global context object.

The global context is initialized as

{
 "lot":
    {
         "total":0,
         "free":0,
         "occupied":0,
         "cams":[]
     }
}

When an HTTP request happens I need to add an object to the global context cams. I try to do this using a change node with Set context.lot.cams to the following JSONATA:

$append(global.context.lot.cams, 

        {$string(msg.req.params.cam) :
        {"total" : msg.req.body.totalLots,
        "free" : msg.req.body.totalLots - msg.req.body.occupied,
        "occupied" : msg.req.body.occupied}
        }

)

However instead of appending it overwrites the cams array with the new element.

How to append a custom object built using http request parameters to a global context array in node-red?

score 1 · Answer 1 · answered Jul 21 '18 at 21:40

The easiest way to do this would be a Function node. Based on what you've shared, something along the lines of the following would do it:

var myData = global.get("context.lot.cams");
var newObj = {};
newObj[msg.req.params.cam] = {
  "total" : msg.req.body.totalLots,
  "free" : msg.req.body.totalLots - msg.req.body.occupied,
  "occupied" : msg.req.body.occupied
};
myData.push(newObj);
global.set("context.lot.cams",newObj);
return msg;

How to append a custom object built from http request parameters to a global context array in node-red?

1 Answers1