How to get single key from array of array in javascript?

Question

I have a structure like

  const test = [
    {
      items: [
        {
          id: "tete",
        },
        {
          id: "tete",
        },
      ],
    },
    {
      items: [
        {
          id: "tete",
        },
      ],
    },
  ];

How go i get all the 'id' value from these array using javascript.

You could use a combination of reduce and map, such as: const ids = test.reduce((a, b) => [...a, ...b.items.map(c => c.id)], []). you can look at the documentation for these functions on the MDN reduce and map — Jacob Smit
– Jacob Smit, Commented Nov 10, 2022 at 20:30

k.tten · Accepted Answer · 2022-11-10 20:32:07Z

1

The new flatMap can do it all in one line with the regular map:

const test = [{items:[{id:"tete",},{id:"tete",},],},{items:[{id:"tete"}]}];

const result = test.flatMap((e) => e.items.map((i) => i.id));

console.log(result);

It is equivalent to the following:

const result = test.map((e) => e.items.map((i) => i.id)).flat();

answered Nov 10, 2022 at 20:32

k.tten

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1 Comment

c0m1t Over a year ago

If you want to remove duplicates, you could use Set after you got all the ids.

Jagrut Sharma · Accepted Answer · 2022-11-10 20:39:34Z

0

This is one option to extract the id values:

const test = [
    {
        items: [
            {
                id: "tete",
            },
            {
                id: "tete",
            },
        ],
    },
    {
        items: [
            {
                id: "tete",
            },
        ],
    },
];

const ids = test.reduce((acc, element) => {
    for (const item of element.items) {
        acc.push(item.id);
    }
    return acc;
}, []);

console.log(ids);

answered Nov 10, 2022 at 20:39

Jagrut Sharma

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1 Comment

k.tten Over a year ago

one-liner for the callback: acc.concat(element.items.map(({ id }) => id)))

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