How to replace key/value pairs in an object of two arrays of objects

Question

I would like to replace the key 'id' and it's value with the property of 'type' with a value of 'inc'or 'exp'. I also want to delete the property 'percentage' from the objects in the exp array. In the end I want to merge al the objects into one array.

This is what I did, it has the desired outcome but there must be a shortcut to achieve this, with less code and cleaner. Thanks!

const list = {
     exp: [
       { id: 0, value: 57, percentage: 12 },
       { id: 1, value: 34, percentage: 10 },
    ],
     inc: [
       { id: 1, value: 18 },
       { id: 1, value: 89 },
    ],
};

// Deep copy of list object
let newList = JSON.parse(JSON.stringify(list));

// Destructuring
const { exp, inc } = newList;

for (let obj of exp) {
  obj.type = "exp";
  delete obj.id;
  delete obj.percentage;
}

for (let obj2 of inc) {
  obj2.type = "inc";
  delete obj2.id;
}

//Spread operator
newList = [...newList.exp, ...newList.inc];
console.log(newList);

hgb123 · Accepted Answer · 2021-01-08 08:50:33Z

You could use flatMap in the support of Object.entries()

const list = {
  exp: [
    { id: 0, value: 57, percentage: 12 },
    { id: 1, value: 34, percentage: 10 },
  ],
  inc: [
    { id: 1, value: 18 },
    { id: 1, value: 89 },
  ],
};

const res = Object.entries(list).flatMap(([type, values]) =>
  values.map((value) => ({
    value: value.value,
    type: type,
  }))
);

console.log(res);

Step by step

A = Object.entries(list)

// -->

[
  [
    "exp",
    [
      { "id": 0, "value": 57, "percentage": 12 },
      { "id": 1, "value": 34, "percentage": 10 }
    ]
  ],
  [
    "inc",
    [
      { "id": 1, "value": 18 },
      { "id": 1, "value": 89 }
    ]
  ]
]

B = A.map(...)

// -->

[
  [
    { "value": 57, "type": "exp" },
    { "value": 34, "type": "exp" }
  ],
  [
    { "value": 18, "type": "inc" },
    { "value": 89, "type": "inc" }
  ]
]

C = B.flat()

// -->

[
  { "value": 57, "type": "exp" },
  { "value": 34, "type": "exp" },
  { "value": 18, "type": "inc" },
  { "value": 89, "type": "inc" }
]

flatMap is the combination of step B and C (.map then .flat)

Mark Feng · Accepted Answer · 2021-01-08 08:49:21Z

1

If value is the only property you want:

const list = {
  exp: [
    { id: 0, value: 57, percentage: 12 },
    { id: 1, value: 34, percentage: 10 }
  ],
  inc: [
    { id: 1, value: 18 },
    { id: 1, value: 89 }
  ]
};

const newList = [];
const types = Object.keys(list);
types.forEach((type) => {
  list[type].forEach(({ value }) => {
    newList.push({ type, value });
  });
});

console.log(newList);
console.log(JSON.stringify(newList));

answered Jan 8, 2021 at 8:49

Mark Feng

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