Filtering array of nested objects

Question

The following code is producing the desired output but I'm wondering if there's a way to accomplish the same result by applying .filter() to data. Any other more concise approaches than shown below are also welcomed.

Data description: scenarios consist of a scenario object plus an array of profile objects

Filtering goal: keep scenarios that have flag = 1 and probability > 0.9

    const data = [
        {
            "scenario": {
                "scenarioId": 41511,
                "flag": 1,
                "probability": 0.92
            },
            "profile": [
                {
                    "profileId": 1,
                    "scenarioId": 41511,
                    "capacity": 0.77
                },
                {
                    "profileId": 2,
                    "scenarioId": 41511,
                    "capacity": 0.74
                }
            ]
        },
        {
            "scenario": {
                "scenarioId": 41521,
                "flag": 1,
                "probability": 0.8
            },
            "profile": [
                {
                    "profileId": 3,
                    "scenarioId": 41521,
                    "capacity": 0.96
                }
            ]
        },
        {
            "scenario": {
                "scenarioId": 41530,
                "flag": 0,
                "probability": 0.95
            },
            "profile": [
                {
                    "profileId": 4,
                    "scenarioId": 41530,
                    "capacity": 0.73
                },
                {
                    "profileId": 5,
                    "scenarioId": 41530,
                    "capacity": 0.92
                }
            ]
        },
        {
            "scenario": {
                "scenarioId": 41540,
                "flag": 0,
                "probability": 0.85
            },
            "profile": [
                {
                    "profileId": 6,
                    "scenarioId": 41540,
                    "capacity": 0.88
                }
            ]
        },
        {
            "scenario": {
                "scenarioId": 41551,
                "flag": 1,
                "probability": 1
            },
            "profile": [
                {
                    "profileId": 7,
                    "scenarioId": 41551,
                    "capacity": 0.88
                },
                {
                    "profileId": 8,
                    "scenarioId": 41551,
                    "capacity": 0.99
                }
            ]
        },
    ];

    const keepers = {};
    for (i of data) {
        if (i.scenario.flag == 1 && i.scenario.probability > 0.9) {
            keepers[i.scenario.scenarioId] = { ...i.scenario, profile: i.profile };
        }
    }

    console.log(keepers);

Toby Speight · Accepted Answer · 2022-12-05 16:16:04Z

Use filter to select a subset of elements. Use map to map all the elements from one type to another. Your program is a case for combination of both. For efficiency reasons, filter first so that you don't map elements you are not interested in.

Don't use semicolons in js. They are not needed and it gets inconsistent if you forget them somewhere but the program still works.

You can also use destructuring of the arguments to get rid of the dummy i.

Also prefer strict comparison. In this case for the flag scenario.flag === 1

const data = [{"scenario":{"scenarioId":41511,"flag":1,"probability":0.92},"profile":[{"profileId":1,"scenarioId":41511,"capacity":0.77},{"profileId":2,"scenarioId":41511,"capacity":0.74}]},{"scenario":{"scenarioId":41521,"flag":1,"probability":0.8},"profile":[{"profileId":3,"scenarioId":41521,"capacity":0.96}]},{"scenario":{"scenarioId":41530,"flag":0,"probability":0.95},"profile":[{"profileId":4,"scenarioId":41530,"capacity":0.73},{"profileId":5,"scenarioId":41530,"capacity":0.92}]},{"scenario":{"scenarioId":41540,"flag":0,"probability":0.85},"profile":[{"profileId":6,"scenarioId":41540,"capacity":0.88}]},{"scenario":{"scenarioId":41551,"flag":1,"probability":1},"profile":[{"profileId":7,"scenarioId":41551,"capacity":0.88},{"profileId":8,"scenarioId":41551,"capacity":0.99}]}];

const keepers = data
    .filter(({ scenario }) => scenario.flag === 1 && scenario.probability > 0.9)
    .map(({ scenario, profile }) => { return { ...scenario, profile } })

console.log(keepers)

Can you insert the code as a runnable code snippet? That would be helpful. — knot22
– knot22, Commented Dec 4, 2022 at 17:31

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