How can i return two objects in javascript

Question

As an example

I have two arrays

const tempData = [
          { day: "Mon", temp: 33.6 },
          { day: "Tue", temp: 34.6 },
          { day: "Wed", temp: 33.1 },
          { day: "Fri", temp: 35.6 }
        ];
const coughData = [
          { day: "Mon", count: 2 },
          { day: "Wed", count: 1 },
          { day: "Thur", count: 1 },
          { day: "Fri", count: 3 },
          { day: "Sat", count: 1 }
        ];

I need to merge these arrays into one so that if the day matches the count value adds to that object if it doesn't match it adds both objects to the array.

Don't know if the explanation isn't so clear but

The expected result should be like this:

const data = [
          { day: "Mon", temp: 33.6, count: 2 },
          { day: "Tue", temp: 34.6 },
          { day: "Wed", temp: 33.1, count: 1 },
          { day: "Thur", count: 1 },
          { day: "Fri", temp: 35.6, count: 3 },
          { day: "Sat", count: 1 }
        ];

I am trying to use map function like so but can't understand how do I return both the objects if they don't match:

const data = tempData.map(temp => {
          coughData.map(cough => {
            if (temp.day === cough.day) {
              return (temp.count = cough.count);
            } else {
              return cough;
            }
          });
          return temp;
        });

Array.map will transform array rows, it's name is map, So you have to use Array.reduce. — Vahid Alimohamadi
– Vahid Alimohamadi, Commented Dec 24, 2020 at 12:43

Nina Scholz · Accepted Answer · 2020-12-24 12:49:58Z

4

You could collect all data grouped by day in an object and get the values as result set.

const
    addToCollection = (collection, key) => o => Object.assign(collection[o[key]] ??= {}, o),
    tempData = [{ day: "Mon", temp: 33.6 }, { day: "Tue", temp: 34.6 }, { day: "Wed", temp: 33.1 }, { day: "Fri", temp: 35.6 }],
    coughData = [{ day: "Mon", count: 2 }, { day: "Wed", count: 1 }, { day: "Thur", count: 1 }, { day: "Fri", count: 3 }, { day: "Sat", count: 1 }],
    collection = {};
    
tempData.forEach(addToCollection(collection, 'day'));
coughData.forEach(addToCollection(collection, 'day'));

console.log(Object.values(collection));

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Dec 24, 2020 at 12:49

Nina Scholz

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Nick Parsons · Accepted Answer · 2020-12-24 12:59:08Z

2

You can first merge the objects of the arrays, and then use .reduce() along with a Map to accumulate the values. The Map can be keyed by the day property, which will allow you to group related object properties together. You can then use Array.from() to transform your Map back into an array of objects like so:

const tempData = [{ day: "Mon", temp: 33.6 }, { day: "Tue", temp: 34.6 }, { day: "Wed", temp: 33.1 }, { day: "Fri", temp: 35.6 }];
const coughData = [{ day: "Mon", count: 2 }, { day: "Wed", count: 1 }, { day: "Thur", count: 1 }, { day: "Fri", count: 3 }, { day: "Sat", count: 1 }];

const arr = [...tempData, ...coughData];

const result = Array.from(arr.reduce((map, {day, ...rest}) => {
  const seen = map.get(day) || {day};
  return map.set(day, {...seen, ...rest});
}, new Map).values());

console.log(result);

edited Dec 24, 2020 at 12:59

answered Dec 24, 2020 at 12:55

Nick Parsons

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2 Comments

adiga Over a year ago

If you add a day key instead of empty object literal here: map.get(day) || { day }, you can get Array.from(mapFromReduce.values()). No need for the additional operation of ([day, obj]) => ({day, ...obj})

Nick Parsons Over a year ago

@adiga Nice, that's much nicer, thanks :D

ValeriF21 · Accepted Answer · 2020-12-24 13:08:17Z

0

let newArray = Array();
let longer = (tempData.length <= coughData.length) ? coughData.length : 
tempData.length;
for(let i = 0, j = 0; i < longer; ++i, ++j) {
    newArray.push(Object.assign(coughData[i], tempData[j]));
}

Print to console:

[ { day: 'Mon', count: 2, temp: 33.6 },
{ day: 'Tue', count: 1, temp: 34.6 },
{ day: 'Wed', count: 1, temp: 33.1 },
{ day: 'Fri', count: 3, temp: 35.6 },
{ day: 'Sat', count: 1 } ]

answered Dec 24, 2020 at 13:08

ValeriF21

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Nilesh Patel · Accepted Answer · 2020-12-24 13:15:01Z

0

const tempData = [
    { day: "Mon", temp: 33.6 },
    { day: "Tue", temp: 34.6 },
    { day: "Wed", temp: 33.1 },
    { day: "Fri", temp: 35.6 }
];
const coughData = [
    { day: "Mon", count: 2 },
    { day: "Wed", count: 1 },
    { day: "Thur", count: 1 },
    { day: "Fri", count: 3 },
    { day: "Sat", count: 1 }
];

const tempRes = [...tempData, ...coughData];
const result = tempRes.reduce((acc, curr) => {
    const { day, ...rest } = curr;
    acc[day] = acc[day] ? Object.assign({}, acc[day], rest) : curr
    return acc;
}, {})
console.log(Object.values(result))

.as-console-wrapper { max-height: 100% !important; top: 0; }

answered Dec 24, 2020 at 13:15

Nilesh Patel

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marcelo colombo · Accepted Answer · 2020-12-24 12:47:33Z

-4

You can use Object.assign() javascript function. The Object.assign () method is used to copy the values of all the enumerable properties of one or more source objects to a target object. This method will return the target object

Like so:

const target = { a: 1, b: 2 };
const source = { b: 4, c: 5 };

const returnedTarget = Object.assign(target, source);

console.log(target);
// expected output: Object { a: 1, b: 4, c: 5 }

console.log(returnedTarget);
// expected output: Object { a: 1, b: 4, c: 5 }

https://developer.mozilla.org/pt-BR/docs/Web/JavaScript/Reference/Global_Objects/Object/assign

answered Dec 24, 2020 at 12:47

marcelo colombo

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