How to create key value pair from an array?

Question

I have an array object with following data:

const arr = [
{
  key: 'mykey1597855209',
  integrity: 'sha512-T9JWj=='
},
{
  key: 'mykey159785520915978552101597855212',
  integrity: 'sha512-T9JWj=='
},
{
  key: 'mykey15978552091597855210',
  integrity: 'sha512-lcddfd=='
},
{
  key: 'otherkey15978552091597855210',
  integrity: 'sha512-abcdfd=='
}];

I want to create key value pair from the the arr[] object such that integrity becomes key and the key becomes value

Desired Output is something like below:

{
  "sha512-T9JWj==": [
    "mykey1597855209",
    "mykey159785520915978552101597855212"
  ],
  "sha512-lcddfd==": [
    "mykey15978552091597855210"
  ],
  "sha512-abcdfd==": [
    "otherkey15978552091597855210"
  ]
}

I have written following code:

 const arr = [{ key: 'mykey1597855209', integrity: 'sha512-T9JWj==' }, { key: 'mykey159785520915978552101597855212', integrity: 'sha512-T9JWj==' }, { key: 'mykey15978552091597855210', integrity: 'sha512-lcddfd==' }, { key: 'otherkey15978552091597855210', integrity: 'sha512-abcdfd==' } ]; const result = Object.assign(...arr.map(a => ({ [a.integrity]: a.key }))); console.log(result)

Answer 1

You can transform it like this:

let map = {};

arr.forEach({ key, integrity } => map[integrity] = key);

Answer 2

You can use Object.fromEntries :

 const arr = [{key: 'mykey1597855209',integrity: 'sha512-T9JWj=='},{key: 'mykey159785520915978552101597855212',integrity: 'sha512-T9JWj=='},{key: 'mykey15978552091597855210',integrity: 'sha512-lcddfd=='},{key: 'otherkey15978552091597855210',integrity: 'sha512-abcdfd=='}]; let map = Object.fromEntries(arr.map(({_, integrity }) => [integrity, []])); arr.forEach(({key, integrity}) => map[integrity].push(key)); console.log(map);

Or reduce :

 const arr = [{key: 'mykey1597855209',integrity: 'sha512-T9JWj=='},{key: 'mykey159785520915978552101597855212',integrity: 'sha512-T9JWj=='},{key: 'mykey15978552091597855210',integrity: 'sha512-lcddfd=='},{key: 'otherkey15978552091597855210',integrity: 'sha512-abcdfd=='}]; let map = arr.reduce((acc, { key, integrity }) => { acc[integrity] = acc[integrity] || []; acc[integrity].push(key); return acc; }, {}); console.log(map);

Answer 3

arr.reduce((acc, curr) => {    
    acc[curr.integrity] = (acc[curr.integrity]) ? 
                          [ ...acc[curr.integrity], curr.key ] : 
                          [ curr.key ]    
    return acc;
}, {})