What is the best way to merge the values of an array within an array of objects with the same property in JavaScript?

Question

What is the best way to merge the values of an array within an array of objects with the same property in JavaScript?

Check out the array below:

const a = [
  {
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  }
]

Is there a function available that can merge arrays with identical keys within an object?

`const result = [{
26: [0,0,0],
27: [100,100,100],
28: [0,0,0]
}]`

javascript arrays algorithm data-structures javascript-objects

Answer 1

Answer №1

Consider utilizing the reduce method

const information = [{
    26: [0], 27: [100], 28: [0]
  },
  {
    26: [0], 27: [100], 28: [0]
  },
  {
    26: [0], 27: [100], 28: [0]
  }
];

const organizeData = arr => 
  [arr.reduce((accumulator, current) => {
    for (const [key, value] of Object.entries(current)) {
      accumulator[key] = [...accumulator[key] ?? '', ...value];
    }
    return accumulator;
  }, {})];

console.log(JSON.stringify(organizeData(information)));

Answer 2

Consider utilizing the reduce method

const information = [{
    26: [0], 27: [100], 28: [0]
  },
  {
    26: [0], 27: [100], 28: [0]
  },
  {
    26: [0], 27: [100], 28: [0]
  }
];

const organizeData = arr => 
  [arr.reduce((accumulator, current) => {
    for (const [key, value] of Object.entries(current)) {
      accumulator[key] = [...accumulator[key] ?? '', ...value];
    }
    return accumulator;
  }, {})];

console.log(JSON.stringify(organizeData(information)));

Answer 3

Answer №2

To achieve this task, you can make use of the Array.forEach() method in JavaScript.

Here is a simple demonstration:

const data = [{
  26: [0],
  27: [100],
  28: [0]
}, {
  26: [0],
  27: [100],
  28: [0]
}, {
  26: [0],
  27: [100],
  28: [0]
}];

let resultObject = {};

data.forEach(item => {
    Object.keys(item).forEach(key => {
    resultObject[key] ? resultObject[key].push(...item[key]) : resultObject[key] = [...item[key]]
  })
});

console.log([resultObject]);

Answer 4

To achieve this task, you can make use of the Array.forEach() method in JavaScript.

Here is a simple demonstration:

const data = [{
  26: [0],
  27: [100],
  28: [0]
}, {
  26: [0],
  27: [100],
  28: [0]
}, {
  26: [0],
  27: [100],
  28: [0]
}];

let resultObject = {};

data.forEach(item => {
    Object.keys(item).forEach(key => {
    resultObject[key] ? resultObject[key].push(...item[key]) : resultObject[key] = [...item[key]]
  })
});

console.log([resultObject]);

Answer 5

Answer №3

Having a set of utility functions on hand can greatly simplify tackling this type of problem.

The approach I take is to create the following function:

const combine = reduce (mergeWith (concat)) ({})

This function is built using my utility functions reduce, concat, and mergeWith. Using it is as straightforward as:

combine (a) //=> {26: [0, 0, 0], 27: [100, 100, 100], 28: [0, 0, 0]}

const reduce = (f) => (init) => (xs) => xs .reduce ((a, x) => f (a, x), init)
const concat = (a) => (b) => a .concat (b)
const mergeWith = (f) => (a, b) => Object .fromEntries (
  [... new Set ([... Object .keys (a), ... Object .keys (b)])] .map (
    (k) => [k, k in a ? (k in b ? f (a [k]) (b [k]) : a [k]) : b [k]]
  )
)

const combine = reduce (mergeWith (concat)) ({}) 

const a = [{26: [0], 27: [100], 28: [0]}, {26: [0], 27: [100], 28: [0]}, {26: [0], 27: [100], 28: [0]}]

console .log (combine (a))

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

reduce and concat essentially convert array methods into pure functions.¹ They are fully curried, making it easier to compose functions by calling them with multiple arguments instead of using method chaining.

mergeWith function performs a shallow merge between two objects, utilizing a provided function when keys match in both objects, and using the supplied property otherwise.

By setting up these utility functions in advance, writing the solution becomes quite straightforward. We configure mergeWith with concat and pass them along with an empty object to reduce.

const combine = reduce (mergeWith (concat)) ({})

^{¹reduce does not provide all parameters to the transformation function that Array.prototype.reduce does. This design choice has its reasons, but if desired, we could simplify the implementation to}

const reduce (f) => (init) => (xs) => xs .reduce (f, init)

.

Answer 6

Having a set of utility functions on hand can greatly simplify tackling this type of problem.

The approach I take is to create the following function:

const combine = reduce (mergeWith (concat)) ({})

This function is built using my utility functions reduce, concat, and mergeWith. Using it is as straightforward as:

combine (a) //=> {26: [0, 0, 0], 27: [100, 100, 100], 28: [0, 0, 0]}

const reduce = (f) => (init) => (xs) => xs .reduce ((a, x) => f (a, x), init)
const concat = (a) => (b) => a .concat (b)
const mergeWith = (f) => (a, b) => Object .fromEntries (
  [... new Set ([... Object .keys (a), ... Object .keys (b)])] .map (
    (k) => [k, k in a ? (k in b ? f (a [k]) (b [k]) : a [k]) : b [k]]
  )
)

const combine = reduce (mergeWith (concat)) ({}) 

const a = [{26: [0], 27: [100], 28: [0]}, {26: [0], 27: [100], 28: [0]}, {26: [0], 27: [100], 28: [0]}]

console .log (combine (a))

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

reduce and concat essentially convert array methods into pure functions.¹ They are fully curried, making it easier to compose functions by calling them with multiple arguments instead of using method chaining.

mergeWith function performs a shallow merge between two objects, utilizing a provided function when keys match in both objects, and using the supplied property otherwise.

By setting up these utility functions in advance, writing the solution becomes quite straightforward. We configure mergeWith with concat and pass them along with an empty object to reduce.

const combine = reduce (mergeWith (concat)) ({})

^{¹reduce does not provide all parameters to the transformation function that Array.prototype.reduce does. This design choice has its reasons, but if desired, we could simplify the implementation to}

const reduce (f) => (init) => (xs) => xs .reduce (f, init)

.

Answer 7

Answer №4

One way to accomplish this task is by utilizing the built-in Array.Prototype.map() method in JavaScript.

Here is a sample solution:

function mergeSameKeys(arr) {
    let filteredObj = {}

    arr.map(obj => {
        let objKeys = Object.keys(obj);

        objKeys.map(key => {
            if (!filteredObj.hasOwnProperty(key)) {
                filteredObj[key] = obj[key]
            } else {
                filteredObj[key].push(...obj[key])
            }
        })

    })

    return [filteredObj]
}

mergeSameKeys([{
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  }
])

// returns [{
// 26: [0,0,0],
// 27: [100,100,100],
// 28: [0,0,0]
// }]

The above function iterates through each item in the given array. For each object, it extracts all the keys using Object.keys(), storing them in objKeys. It then loops through each key in objKeys and checks if that key already exists in the filteredObj variable. If not, it adds the key along with its value to filteredObj. If the key is present, it merges the values from the original object and the filteredObj using the Spread syntax (...). The function ultimately returns the filteredObj in an array. This completes the code implementation.

Answer 8

One way to accomplish this task is by utilizing the built-in Array.Prototype.map() method in JavaScript.

Here is a sample solution:

function mergeSameKeys(arr) {
    let filteredObj = {}

    arr.map(obj => {
        let objKeys = Object.keys(obj);

        objKeys.map(key => {
            if (!filteredObj.hasOwnProperty(key)) {
                filteredObj[key] = obj[key]
            } else {
                filteredObj[key].push(...obj[key])
            }
        })

    })

    return [filteredObj]
}

mergeSameKeys([{
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  },
  {
    26: [0],
    27: [100],
    28: [0]
  }
])

// returns [{
// 26: [0,0,0],
// 27: [100,100,100],
// 28: [0,0,0]
// }]

The above function iterates through each item in the given array. For each object, it extracts all the keys using Object.keys(), storing them in objKeys. It then loops through each key in objKeys and checks if that key already exists in the filteredObj variable. If not, it adds the key along with its value to filteredObj. If the key is present, it merges the values from the original object and the filteredObj using the Spread syntax (...). The function ultimately returns the filteredObj in an array. This completes the code implementation.

What is the best way to merge the values of an array within an array of objects with the same property in JavaScript?

Answer №1

Answer №2

Answer №3

Answer №4

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