CODEWITHSUNDEEP
javascript
pingeyeg
pingeyeg

Reputation: 680

How to merge two objects containing same keys but different values

I'm wanting to merge two array that carry objects with the same keys, but one object may have a value, but the other object, carrying the same key, may have a null value. I'm wanting to merge the two to try and replace all the null values and have one final object.

I've written the following, but at the moment, I'm only getting undefined as the final result.

const objectOne = [
  {
    one: null,
    two: "Two",
    three: null
  }
];

const objectTwo = [
  {
    one: "One",
    two: null,
    three: "Three"
  }
];

const compareObjects = (searchKey, searchValue) =>
  objectTwo.map((retrieve) =>
    Object.entries(retrieve).forEach(([retrieveKey, retrieveValue]) => {
      if (!searchValue) {
        objectOne.searchKey = retrieveValue;
        console.log(objectOne);
      }
    })
  );

const newObject = objectOne.map((search) =>
  Object.entries(search).forEach(([searchKey, searchValue]) =>
    compareObjects(searchKey, searchValue)
  )
);

console.log(newObject);

Upvotes: 1

Views: 2071

Answers (3)

Aniketh Malyala
Aniketh Malyala

Reputation: 2660

One method you can use is to create a function that combines/merges the two dictionaries. First, we create our newObject:

const newObject = [

]

Then, we create our function using an O(n^2) approach and call it:

combine(objectOne,objectTwo)
console.log(newObject)

function combine(objectOne, objectTwo){
    for (let [key1,value1] of Object.entries(objectOne[0])){
        for (let [key2,value2] of Object.entries(objectTwo[0])){
            if(key1 == key2){
                if(value1 == null){
                    newObject.push({
                        key: key1,
                        value: value2
                    })
                }
                else{
                    newObject.push({
                        key: key1,
                        value: value1
                    })
                }
            }
        }
    }
}

This is the following output:

[
  { key: 'one', value: 'One' },
  { key: 'two', value: 'Two' },
  { key: 'three', value: 'Three' }
]

Upvotes: 0

Charlie Bamford
Charlie Bamford

Reputation: 1309

Reduce seems more useful in this case than forEach. Reduce will build a new thing from the input and return that.

const objectOne = [
  {
    one: null,
    two: "Two",
    three: null
  }
];

const objectTwo = [
  {
    one: "One",
    two: null,
    three: "Three"
  }
];

const merged = objectOne.map((item, idx) => {
  return Object.entries(item).reduce((acc, [key, value]) => {
    acc[key] = value === null && objectTwo.length > idx ? objectTwo[idx][key] : value;
    return acc;
  }, {})
});
console.log(merged);

Upvotes: 2

Kelvin Schoofs
Kelvin Schoofs

Reputation: 8718

Your mapping of keys/entries is pretty close. It might be easiest to do something like this though:

const objectOnes = [
  {
    one: null,
    two: "Two",
    three: null
  },
  {
     a: 123,
     b: undefined,
  },
];

const objectTwos = [
  {
    one: "One",
    two: null,
    three: "Three"
  },
  {
      b: 456,
  }
];

function merge(a, b) {
    const result = { ...a }; // copy a
    for (const key in result) {
        // Let's say we want to pick the non-null/undefined value
        if (result[key] !== null && result[key] !== undefined) continue;
        result[key] = b[key]; // copy from b
    }
    return result;
}

const merged = objectOnes.map((obj, i) => merge(obj, objectTwos[i]));
console.log(merged);

Upvotes: 1

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