Node-RED/Home Assistant: Flow to count number of people at home.

flow.json

[
    {
        "id": "bcba552587aca961",
        "type": "tab",
        "label": "People counter",
        "disabled": false,
        "info": "",
        "env": []
    },
    {
        "id": "14c2c444afcdb504",
        "type": "server-state-changed",
        "z": "bcba552587aca961",
        "name": "",
        "server": "2dc0325926925490",
        "version": 3,
        "exposeToHomeAssistant": false,
        "haConfig": [
            {
                "property": "name",
                "value": ""
            },
            {
                "property": "icon",
                "value": ""
            }
        ],
        "entityidfilter": "^person\\..*$",
        "entityidfiltertype": "regex",
        "outputinitially": true,
        "state_type": "str",
        "haltifstate": "",
        "halt_if_type": "str",
        "halt_if_compare": "is",
        "outputs": 1,
        "output_only_on_state_change": true,
        "for": 0,
        "forType": "num",
        "forUnits": "minutes",
        "ignorePrevStateNull": false,
        "ignorePrevStateUnknown": false,
        "ignorePrevStateUnavailable": false,
        "ignoreCurrentStateUnknown": false,
        "ignoreCurrentStateUnavailable": false,
        "outputProperties": [
            {
                "property": "payload",
                "propertyType": "msg",
                "value": "",
                "valueType": "entityState"
            },
            {
                "property": "data",
                "propertyType": "msg",
                "value": "",
                "valueType": "eventData"
            },
            {
                "property": "topic",
                "propertyType": "msg",
                "value": "",
                "valueType": "triggerId"
            }
        ],
        "x": 170,
        "y": 120,
        "wires": [
            [
                "ca1d8b9a03fc52f0"
            ]
        ]
    },
    {
        "id": "ca1d8b9a03fc52f0",
        "type": "function",
        "z": "bcba552587aca961",
        "name": "Count people at home",
        "func": "// get array of people at home\nlet people_home = context.get('people_home') || [];\n\n// Add person to array\nif (msg.payload === 'home' && !people_home.includes(msg.topic)) {\n    people_home.push(msg.topic);\n}\n\n// Remove person from array\nif (msg.payload !== 'home' && people_home.includes(msg.topic)) {\n    people_home = people_home.filter(item => item !== msg.topic)\n}\n\n// Store array\ncontext.set('people_home', people_home);\n\n// Pass on length of array\nreturn { payload: people_home.length };",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 460,
        "y": 120,
        "wires": [
            [
                "b8e6d0ce4272796d"
            ]
        ]
    },
    {
        "id": "b8e6d0ce4272796d",
        "type": "ha-entity",
        "z": "bcba552587aca961",
        "name": "sensor.number_of_people_home",
        "server": "2dc0325926925490",
        "version": 2,
        "debugenabled": false,
        "outputs": 1,
        "entityType": "sensor",
        "config": [
            {
                "property": "name",
                "value": "number_of_people_home"
            },
            {
                "property": "device_class",
                "value": ""
            },
            {
                "property": "icon",
                "value": "mdi:person"
            },
            {
                "property": "unit_of_measurement",
                "value": ""
            },
            {
                "property": "state_class",
                "value": ""
            },
            {
                "property": "last_reset",
                "value": ""
            }
        ],
        "state": "payload",
        "stateType": "msg",
        "attributes": [],
        "resend": true,
        "outputLocation": "payload",
        "outputLocationType": "none",
        "inputOverride": "allow",
        "outputOnStateChange": false,
        "outputPayload": "$entity().state ? \"on\": \"off\"",
        "outputPayloadType": "jsonata",
        "x": 760,
        "y": 120,
        "wires": [
            []
        ]
    },
    {
        "id": "2dc0325926925490",
        "type": "server",
        "name": "Home Assistant: Development Server",
        "version": 2,
        "addon": false,
        "rejectUnauthorizedCerts": true,
        "ha_boolean": "y|yes|true|on|home|open",
        "connectionDelay": true,
        "cacheJson": true,
        "heartbeat": false,
        "heartbeatInterval": "30"
    }
]