Ways to decrease and transform a collection of objects?

Question

Ways to decrease and transform a collection of objects?

What is the best way to condense and transform this object array into a new array?

Here is the data I am working with:

var objArray = 
  [{
    state: 'NY',
    type: 'A',
    population: 100
  },
  {
    state: 'NY',
    type: 'A',
    population: 300
  },
  {
    state: 'NY',
    type: 'B',
    population: 200
  },
  {
    state: 'CA',
    type: 'A',
    population: 400
  },
  {
    state: 'CA',
    type: 'A',
    population: 400
  }];

In cases where an entry shares both the same state AND type, I want to merge them into one entry while adding up their populations.

Finally, I aim to map this condensed data into an array structured like this:

 var outputArray = [ ['A', 'NY', 400 ], ['B', 'NY', 200], ['A', 'CA', 800] ]

javascript arrays

Answer 1

Answer №1

To start, the initial step would be to decrease it. This process can be achieved in the following manner...

objArray.reduce((prev, obj) => {
    if(1 + (indx = prev.findIndex(oldObj => oldObj.type === obj.type && oldObj.state === obj.state))) {
        prev[indx].population += obj.population;
    } else {
        prev.push({...obj})
    }
    return prev;
}, [])

This operation manipulates the gathered array by making modifications and returns it within the reduce callback function. It will either adjust an existing value's population if a matching one with the correct state and type is found, or append a new object at the end of the array.

Next, you must proceed to perform mapping on it.

.map(obj => [ obj.type, obj.state, obj.population ])

Answer 2

To start, the initial step would be to decrease it. This process can be achieved in the following manner...

objArray.reduce((prev, obj) => {
    if(1 + (indx = prev.findIndex(oldObj => oldObj.type === obj.type && oldObj.state === obj.state))) {
        prev[indx].population += obj.population;
    } else {
        prev.push({...obj})
    }
    return prev;
}, [])

This operation manipulates the gathered array by making modifications and returns it within the reduce callback function. It will either adjust an existing value's population if a matching one with the correct state and type is found, or append a new object at the end of the array.

Next, you must proceed to perform mapping on it.

.map(obj => [ obj.type, obj.state, obj.population ])

Answer 3

Answer №2

If you're looking to enhance your Javascript applications, I highly recommend incorporating the lodash package. This widely-used package offers an array of useful functions for array manipulation. Check out this helpful post on using lodash to sum values based on groups. To adapt the code snippet for your specific parameters, simply update the groupBy command as follows:

_.groupBy(objArray, function(val){
    return val.state + "#" + val.type
})

Answer 4

If you're looking to enhance your Javascript applications, I highly recommend incorporating the lodash package. This widely-used package offers an array of useful functions for array manipulation. Check out this helpful post on using lodash to sum values based on groups. To adapt the code snippet for your specific parameters, simply update the groupBy command as follows:

_.groupBy(objArray, function(val){
    return val.state + "#" + val.type
})

Answer 5

Answer №3

Here is a possible solution:

const newArray = Object.keys(objArray).map(function (key) { return Object.keys(objArray[key]).map(function (key) { return [[objArray[0].country, objArray[0].city, objArray[0].population],[objArray[1].country, objArray[1].city, objArray[1].population]]}); })[0][0];

Answer 6

Here is a possible solution:

const newArray = Object.keys(objArray).map(function (key) { return Object.keys(objArray[key]).map(function (key) { return [[objArray[0].country, objArray[0].city, objArray[0].population],[objArray[1].country, objArray[1].city, objArray[1].population]]}); })[0][0];

Answer 7

Answer №4

In the scenario where you are certain that the state and type values will never contain a specific character like '_', you can combine them to create a unique key, similar to a composite key in a database. For instance, you could use 'NY_A' as a composite key. By organizing an object with these unique keys, summing up the populations, and ultimately breaking them down into an array:

Object.entries(
    objArray.reduce((acc,curr) => (
    acc[curr.type + '_' + curr.state] = curr.population + (acc[curr.type + '_' + curr.state] || 0)
    , acc), {}))
.map(item => [...item[0].split('_'), item[1]])

Answer 8

In the scenario where you are certain that the state and type values will never contain a specific character like '_', you can combine them to create a unique key, similar to a composite key in a database. For instance, you could use 'NY_A' as a composite key. By organizing an object with these unique keys, summing up the populations, and ultimately breaking them down into an array:

Object.entries(
    objArray.reduce((acc,curr) => (
    acc[curr.type + '_' + curr.state] = curr.population + (acc[curr.type + '_' + curr.state] || 0)
    , acc), {}))
.map(item => [...item[0].split('_'), item[1]])

Answer 9

Answer №5

const _ = require('lodash')

const data = [
  { region: 'NY', category: 'A', population: 100 },
  { region: 'NY', category: 'A', population: 300 },
  { region: 'NY', category: 'B', population: 200 },
  { region: 'CA', category: 'A', population: 400 },
  { region: 'CA', category: 'A', population: 400 }
]

const expectedResults = [
  ['A', 'NY', 400],
  ['B', 'NY', 200],
  ['A', 'CA', 800]
]

const calculatedResults = _(data)
  .groupBy(({ region, category }) => [region, category].join(':'))
  .mapValues((regions) => regions.reduce((totalPop, { population }) => totalPop + population, 0))
  .map((populationTotal, regionCategory) => {
    const [region, category] = regionCategory.split(':')
    return [category, region, populationTotal]
  })
  .value()

console.log("Expected Results:")
console.log(expectedResults)
console.log("Calculated Results:")
console.log(calculatedResults)

Answer 10

const _ = require('lodash')

const data = [
  { region: 'NY', category: 'A', population: 100 },
  { region: 'NY', category: 'A', population: 300 },
  { region: 'NY', category: 'B', population: 200 },
  { region: 'CA', category: 'A', population: 400 },
  { region: 'CA', category: 'A', population: 400 }
]

const expectedResults = [
  ['A', 'NY', 400],
  ['B', 'NY', 200],
  ['A', 'CA', 800]
]

const calculatedResults = _(data)
  .groupBy(({ region, category }) => [region, category].join(':'))
  .mapValues((regions) => regions.reduce((totalPop, { population }) => totalPop + population, 0))
  .map((populationTotal, regionCategory) => {
    const [region, category] = regionCategory.split(':')
    return [category, region, populationTotal]
  })
  .value()

console.log("Expected Results:")
console.log(expectedResults)
console.log("Calculated Results:")
console.log(calculatedResults)

Ways to decrease and transform a collection of objects?

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

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