Merge objects inside arrays, which are inside an array

Question

currently I have a little problem, which I am not quite able to solve. I have an array, which can contain single, or more arrays, which than can contain multiple objects. So for instance:

const arr = [
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ],
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ]
]

And I want to merge the objects based on a specific property (here "value") into an array, so that my result will look like that:

const result = ["value A", "value B", "value C", "value A", "value B", "value C"]

Someone got an idea for that? Thank you!

Can you confirm your expected output, please? You wrote const result = {"value A", "value B", "value C", "value A", "value B", "value C"} (which is not valid JS) altought I assume you meant const result = ["value A", "value B", "value C", "value A", "value B", "value C"] — secan
– secan, Commented Feb 3, 2021 at 10:49
Your result is not possible as you depict an object with only values and no keys. Did you mean to use an array? — Emiel Zuurbier
– Emiel Zuurbier, Commented Feb 3, 2021 at 10:50
Ooopsie, yeah, my result should be an array of course. Thanks! — dbljn
– dbljn, Commented Feb 3, 2021 at 10:53

Andre Marasca · Accepted Answer · 2021-02-03 10:51:04Z

3

const arr = [
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ],
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ]
]

let x = arr.flat().map(v=>v.value);

console.log(x);

answered Feb 3, 2021 at 10:51

Andre Marasca

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1 Comment

dbljn Over a year ago

Dude, thats awesome! Works like a charm. I have to look into, what flat actually does. Thank you :)

MorKadosh · Accepted Answer · 2021-02-03 10:51:20Z

0

I believe your desired result is an array, and not object. The output example of yours is invalid.

Anyway, use simple reduce:

const arr = [
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ],
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ]
]

const result = arr.reduce((acc, cur) => {
  const values = cur.map(({value}) => value);
  return acc.concat(values)
}, []);

console.log(result);

answered Feb 3, 2021 at 10:51

MorKadosh

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Comments

SoulKa · Accepted Answer · 2021-02-03 10:51:28Z

0

Like this?

const arr = [
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ],
  [
    {
      "value": "value A"
    },
    {
      "value": "value B"
    },
    {
      "value": "value C"
    }
  ]
]

function mergeArray( arr, property ) {
  const res = [];
  for (const innerArr of arr) {
    for (const obj of innerArr) {
      res.push(obj[property]);
    }
  }
  return res;
}

console.log(mergeArray(arr, "value"));

answered Feb 3, 2021 at 10:51

SoulKa

1957 bronze badges

Comments

yunzen · Accepted Answer · 2021-02-03 10:53:28Z

0

I use nested reduce and map methods of the Array.prototype

{
  const arr = [
    [{
        "value": "value A"
      },
      {
        "value": "value B"
      },
      {
        "value": "value C"
      }
    ],
    [{
        "value": "value A"
      },
      {
        "value": "value B"
      },
      {
        "value": "value C"
      }
    ]
  ];
  
  const newArr = arr.reduce((carry, item) => {
     carry.push(...item.map(item2 => item2.value))
     return carry;
  }, [])
  
  console.log(newArr)
}

answered Feb 3, 2021 at 10:53

yunzen

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