how to create array of object in javascript group by specific field?

Question

I have a data like this:

const input = [ {title: 'head', value: a, amount: 10},
                {title: 'head', value: b, amount: 5},
                {title: 'body', value: c, amount: 20} ];

I want to make an array of object literals with data like this:

const output = [{title: 'head',
                 values: [{value: a, amount: 10},
                          {value: b, amount: 5}]
                },
                {title: 'body',
                 values: [{value: a, amount: 20}]
                }];

since I'm not used to javascript, I'm having trouble wrapping values by title. 🥲

plz help me.

I found this thread which is related to your question: stackoverflow.com/questions/40774697/… — AG_1380
– AG_1380, Commented Jul 29, 2022 at 10:17
Does this answer your question? How can I group an array of objects by key? — Islam Y-
– Islam Y-, Commented Jul 29, 2022 at 10:19
I already see those answers, but I need to describe key 'title' instead of using value as a key. but thanks for the links! — rin
– rin, Commented Jul 29, 2022 at 10:24

soupy-norman · Accepted Answer · 2022-07-29 10:29:01Z

3

You can use Set to get the unique values and then map matching entries to the result like this:

const out = [...new Set(input.map(i=>i.title))].map(e=>{
    return {
        title: e,
        values: input.filter(p=>p.title === e).map(p=>{
            return {
                value: p.value,
                amount: p.amount
            };
        })
    };
});

edited Jul 29, 2022 at 10:29

answered Jul 29, 2022 at 10:18

soupy-norman

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