Overriding the default onInput handler

[bartbutenaers]

Hi guys,

I have a noob question about overriding the default oninput handler (see documentation).
I 'think' I do it similar as in the ui-chart node:

        // server-side event handlers
        const evts = {
            onInput: function (msg, send, done) {
                // My custom onInput handler
                ...
            },
            onSocket: {
               ...
            },
            beforeSend: function (msg) {
                ...
            }
        }

        // inform the dashboard UI that we are adding this node
        if (group) {
            group.register(node, config, evts)

But when I inject a message into my node, this happens:

1. The message arrives in my Vue frontend code
2. The beforeSend of my node is called
3. My custom onInput handler above is being called

I had assumed that only 3 would happen, and not 1 and 2. Because 1 and 2 are triggered by the default onInput handler (which I have overridden)? Or perhaps I have not interpreted the documentation correctly?

Based on the msg.topic:

• Some messages only need server side processing, so they don't need to be send to the frontend
• Some messages need to be send to the frontend.

Can you please give me any tips about how I could achieve something like that.

Thanks!! Bart

[joepavitt]

The beforeSend is poorly named- it's actually beforeSendToClient, rather than the send() within the context of Node-RED. So, I would expect the order to be: 2, 3, 1 as you've listed it.

[bartbutenaers]

Hi @joepavitt,

Ah yes I see. In the old dashboard you had:

• beforeEmit which was called before the message was emitted via websocket to the client, so you could change it if required.
• 'beforeSend' which was called before the message was send on the output into the flow.

Now the order seems to be:

1. beforeSend
2. onInput
3. msg-input in the Vue frontend
4. beforeSend

The last one is a bit confusing for me. Seems the beforeSend is called a second time here:

How do we need to take into account that this function is being called in two different locations (i.e. before and after the frontend)? Because if I understand correctly, this function is not only used to preprocess messages before being send to the frontend?

And sorry but I still am not very sure what is the best way to prevent some messages (e.g. with topic xxx) to be pushed to the Vue frontend.

Thanks!!