Example of How to Add Dynamic Connections to Nodes in ComfyUI

a_dynamic.js

/**
 * Make a dynamic Input for ComfyUI
 */

import { app } from "/scripts/app.js"

const _prefix = '➡️'

const TypeSlot = {
    Input: 1,
    Output: 2,
};

const TypeSlotEvent = {
    Connect: true,
    Disconnect: false,
};

const dynamic_connection = (node, index, event, prefix='in_', type='*', names = []
    ) => {
    if (!node.inputs[index].name.startsWith(prefix)) {
        return
    }
    // remove all non connected inputs
    if (event == TypeSlotEvent.Disconnect && node.inputs.length > 1) {
        console.info(`Removing input ${index} (${node.inputs[index].name})`)
        if (node.widgets) {
            const widget = node.widgets.find((w) => w.name === node.inputs[index].name)
            if (widget) {
                widget.onRemoved?.()
                node.widgets.length = node.widgets.length - 1
            }
        }
        node.removeInput(index)

        // make inputs sequential again
        for (let i = 0; i < node.inputs.length; i++) {
            const name = i < names.length ? names[i] : `${prefix}${i + 1}`
            node.inputs[i].label = name
            node.inputs[i].name = name
        }
    }

    // add an extra input
    if (node.inputs[node.inputs.length - 1].link != undefined) {
        const nextIndex = node.inputs.length
        const name = nextIndex < names.length
            ? names[nextIndex]
            : `${prefix}${nextIndex + 1}`

        console.info(`Adding input ${nextIndex + 1} (${name})`)
        node.addInput(name, type)
    }
}

const _id = "<NODES_I_AM_FILTERING>"
const my_extension = {
	name: 'some.unique.name',
	async beforeRegisterNodeDef(nodeType, nodeData, app) {
        if (nodeData.name !== _id) {
            return;
        }

        const onNodeCreated = nodeType.prototype.onNodeCreated
        nodeType.prototype.onNodeCreated = function () {
            const r = onNodeCreated ? onNodeCreated.apply(this, arguments) : undefined
            this.addInput(`${_prefix}_1`, '*')
            return r
        }

        const onConnectionsChange = nodeType.prototype.onConnectionsChange
        nodeType.prototype.onConnectionsChange = function (slotType, slot, event, link_info, data) {
            const me = onConnectionsChange ? onConnectionsChange.apply(this, arguments) : undefined
            if (slotType === TypeSlot.Input) {
                dynamic_connection(this, slot, event, `${_prefix}_`, '*')
                if (event === TypeSlotEvent.Connect && link_info) {
                    const fromNode = this.graph._nodes.find(
                        (otherNode) => otherNode.id == link_info.origin_id
                    )
                    const type = fromNode.outputs[link_info.origin_slot].type
                    this.inputs[slot].type = type
                } else if (event === TypeSlotEvent.Disconnect) {
                    this.inputs[slot].type = '*'
                    this.inputs[slot].label = `${_prefix}_${slot + 1}`
                }
            }
            return me;
        }
    }
}

app.registerExtension(my_extension)