Why is Filter returning an empty array after filtering the values I need?

Question

I'm trying to carry out some flatmapping and filtering on an array of objects, however, I'm not sure why my final result - after filtering, is still displaying the same number of objects where in some of them, the events property has an empty array.

Object to handle (res) variable:

[
    {
        logs: [
                {
                    events: [
                                {
                                    "type": "unbond",
                                    ...
                                },
                                {
                                    "type": "delegate",
                                    ...
                                },
                                {
                                    "type": "someOther",
                                    ...
                                },
                                {
                                    "type": "withdraw_rewards",
                                    ...
                                },
                                {
                                    "type" : "someOtherOther",
                                    ...
                                },
                                ...
                            ]
                }

        timestamp: "someDate"
    },
        {
        logs: [
                {
                    events: [
                                {
                                    "type": "withdraw_commission",
                                    ...
                                },
                                {
                                    "type": "someOtherOtherOther",
                                    ...
                                },
                                {
                                    "type": "someOther",
                                    ...
                                },
                                {
                                    "type": "withdraw_rewards",
                                    ...
                                },
                                {
                                    "type" : "someOtherOther",
                                    ...
                                },
                                ...
                            ]
                }

        timestamp: "someDate"
    },
    ...
]

Result (after item 5, eveything has an empty array in the event_logs prop:

[
    {
        timestamp: "somedate1",
        event_logs: [
                        {
                            ...
                        }
                    ]
    },
        {
        timestamp: "somedate2",
        event_logs: [
                        {
                            ...
                        }
                    ]
    },
        {
        timestamp: "somedate3",
        event_logs: []              //empty
    },
    ...

]

Here is the code I used to carry out the flatmapping and filtering:

const evnts = res.data.tx_responses.map(({timestamp, logs}) => ({
    timestamp,
    event_logs: logs.flatMap(log => log.events)
                    .filter(events => events.type === "delegate" || events.type === "withdraw_rewards" || events.type === "withdraw_commission" || events.type === "unbond")
}));
return evnts;

How can I get rid of those objects with an empty event_logs prop?

Answer 1

You are creating a map of all but not filtering it in the resultant. if you want to remove evens that does not have any event_log in them you can filter them as shown.

    const evnts = res.data.tx_responses.map(({timestamp, logs}) => ({
            timestamp,
            event_logs: logs.flatMap(log => log.events)
                            .filter(events => events.type === "delegate" || events.type === "withdraw_rewards" || events.type === "withdraw_commission" || events.type === "unbond")
        }));
//filter here
        evnts = evnts.filter(event => event.event_logs.length > 0 )
        return evnts;