This is similar to the question How can I group an array of complex objects by key but my data is complex and the solution provided did not work.

const cars = [
    {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2012'
    }, {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2013'
    }, {
        'make': 'ford',
        'model': ['mustang','mustang lx'],
        'year': '2012'
    }, {
        'make': 'ford',
        'model': ['mustang','mustang lp'],
        'year': '2015'
    }, {
        'make': 'kia',
        'model': 'optima',
        'year': '2012'
    },
];

I want to make a new array of car objects that's grouped by make:

{
    'audi': [
        {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2012'
    }, {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2013'
    }
    ],

    'ford': [
        {
        'make': 'ford',
        'model': ['mustang','mustang lx'],
        'year': '2012'
    }, {
        'make': 'ford',
        'model': ['mustang','mustang lp'],
        'year': '2015'
    }
    ],

    'kia': [
        {
        'make': 'kia',
        'model': 'optima',
        'year': '2012'
    }
    ]
}

I tried

   for (let { domain, ...fields } of items) {
        result[domain] = result[domain] || [];
        result[domain].push({ ...fields });
    }

and

    result = items.reduce(function (r, a) {
        r[a.domain] = r[a.domain] || [];
        r[a.domain].push(a);
        return r;
    }, Object.create(null));

the output was

{
    'audi': [
        {
        'make': 'audi',
        'model': [Array],
        'year': '2012'
    }, {
        'make': 'audi',
        'model': [Array],
        'year': '2013'
    }
    ],

    'ford': [
        {
        'make': 'ford',
        'model': [Array],
        'year': '2012'
    }, {
        'make': 'ford',
        'model': [Array],
        'year': '2015'
    }
    ],

    'kia': [
        {
        'make': 'kia',
        'model': 'optima',
        'year': '2012'
    }
    ]
}

CodePudding user response：

You can try this :

let groupBy = (arr, key) => {
    return arr.reduce((rv, x) => {
        (rv[x[key]] = rv[x[key]] || []).push(x);
        return rv;
    }, {});
};

let res = groupBy(cars, 'make');
console.log(res);

// Output :
// {
//     "audi": [
//         {
//             "make": "audi",
//             "model": [
//                 "r8",
//                 "r9"
//             ],
//             "year": "2012"
//         },
//         {
//             "make": "audi",
//             "model": [
//                 "r8",
//                 "r9"
//             ],
//             "year": "2013"
//         }
//     ],
//     "ford": [
//         {
//             "make": "ford",
//             "model": [
//                 "mustang",
//                 "mustang lx"
//             ],
//             "year": "2012"
//         },
//         {
//             "make": "ford",
//             "model": [
//                 "mustang",
//                 "mustang lp"
//             ],
//             "year": "2015"
//         }
//     ],
//     "kia": [
//         {
//             "make": "kia",
//             "model": "optima",
//             "year": "2012"
//         }
//     ]
// }

CodePudding user response：

we can use lodash library to do this

const cars = [
    {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2012'
    }, {
        'make': 'audi',
        'model': ['r8','r9'],
        'year': '2013'
    }, {
        'make': 'ford',
        'model': ['mustang','mustang lx'],
        'year': '2012'
    }, {
        'make': 'ford',
        'model': ['mustang','mustang lp'],
        'year': '2015'
    }, {
        'make': 'kia',
        'model': 'optima',
        'year': '2012'
    },
];

console.log(_.groupBy(cars, d=> d.make))

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