Reduce array of objects into object [duplicate]

Question

I have the following array

data = [
  { name: 'foo', type: 'fizz', val: 9 },
  { name: 'boo', type: 'buzz', val: 3 },
  { name: 'bar', type: 'fizz', val: 4 },
  { name: 'car', type: 'buzz', val: 7 },
];

How do I make it

{
    9: 'foo',
    3: 'boo,
    4: 'bar',
    7: 'car'
}

in ES6.

Thanks in advance!!

Answer 1

Using Array#forEach.

var data = [ { name: 'foo', type: 'fizz', val: 9 }, { name: 'boo', type: 'buzz', val: 3 }, { name: 'bar', type: 'fizz', val: 4 }, { name: 'car', type: 'buzz', val: 7 }, ], 
    res = {};
    data.forEach(v => res[v.val] = v.name);

    console.log(res);

Using Array#reduce.

var data = [ { name: 'foo', type: 'fizz', val: 9 }, { name: 'boo', type: 'buzz', val: 3 }, { name: 'bar', type: 'fizz', val: 4 }, { name: 'car', type: 'buzz', val: 7 }, ],
    res = data.reduce(function(s,a){
      s[a.val] = a.name;
      return s;
    }, {});
  
    console.log(res);

Answer 2

Something like this should work:

const data = [
  { name: 'foo', type: 'fizz', val: 9 },
  { name: 'boo', type: 'buzz', val: 3 },
  { name: 'bar', type: 'fizz', val: 4 },
  { name: 'car', type: 'buzz', val: 7 },
];

const reduced = data.reduce((acc, item) => {
  acc[item.val] = item.name;
  return acc;
}, {});

console.log(reduced);

Answer 3

You could use Object.fromEntries and map arrays with all key/value pairs.

var data = [{ name: 'foo', type: 'fizz', val: 9 }, { name: 'boo', type: 'buzz', val: 3 }, { name: 'bar', type: 'fizz', val: 4 }, { name: 'car', type: 'buzz', val: 7 }],
    object = Object.fromEntries(data.map(({ val, name }) => [val, name]));

console.log(object);